Tool List- www.amazon.com/shop/acservicetech Support- www.patreon.com/acservicetech For those that are looking for the tools used in the videos: (Linked Below) Here is the Link for the newer UEI DL469 Multimeter- amzn.to/2jw4ePJ Here is a link for the Supco Magnet Jumpers amzn.to/2gS4h6z Here is the Link for the newer UEI DL479 Multimeter with temp sensor- amzn.to/2jtsUbJ Here is the link to the 2 pairs of alligator clips- amzn.to/2CtIL5z Here is the Link for the UEI DL389 Multimeter used in the video - amzn.to/2naJr9o Here is the Link for the FieldPiece ST4 Dual Temp Meter- amzn.to/2AhR6ph Here is the Link for the UEI Temp Sensor- amzn.to/2kawAmJ Here is the link for the Irwin Wire Stripper/Cutter/Crimper- amzn.to/2dGTj2V Here is a link to the Stanley 6 in 1 screwdriver- amzn.to/2x7NuaZ Other tool links can be found in the video description section. ACSERVICETECH is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon. All of the ACSERVICETECH Playlists- th-cam.com/channels/OZR-1IqsAer9wzlvFgb4mA.htmlplaylists?view_as=public If you want to support the ACSERVICETECH Channel and receive more HVACR content, check out www.Patreon.com/acservicetech
I have bad memory of this switch. I remember it was copper metal bottom of switch;I did not remove it and damaged the gas valve and thermostat of client. It was -20 and client was angry and complained me and I lost my job. Now I am not in HVAC anymore but i love your videos and your videos really helps me to improve my knowledge and someday work for myself. Please continue.You teach very well.
Thank you very much! it's really nice to see explanation videos on the older technology. I honestly find older furnaces harder to diagnose because I didn't grow up servicing them. So to see in depth explanations on what some may feel is a really simple component is advantageous to technicians that were taught mostly newer tech.
Hi, Thank you for the awesome video. Sometimes changing the thermostat can save you 5k to 10k on this HVAC system (lol). "HVAC CAN BE DANGEROUS; DO NOT ATTEMPT ANY REPAIR IF YOU HAVE NO KNOWLEDGE OF WHAT YOU ARE DOING." I have an old furnace in my house. I had the relay buzzing very loudly inside the furnace. Called the technician he said it was the transformer and relay, and would charge $300 for the relay only (lol). He also advised me to put a new and more efficient HVAC system. Called another one he also told me your system is old get a new one. He told me your furnace and AC are running at the same time (bu**). After he left, I checked the outside unit wasn't running. After that, I decided to take matters into my own hand. I made my own wiring diagram of the furnace system since the older system is simple without any circuit boards. Checked voltage on the transformer, limit switch, relays, and so on. While checking the voltage on the relay coil (magnetize switch ) and it was 3 V instead of 24 V. Since I had the wiring diagram ready I figured out the culprit was a thermostat. I also had to replace thermostat batteries twice that week but it was hard to relate it with relay buzzing since I had no idea of the system before. I replaced the thermostat with a new one since it was in warranty. I am using the smart google Nests thermostat. It took me 3 days to do the above tasks. So in summary, I saved myself 5k to 10 k for the new HVAC system. Good luck with your diagnostics everyone.
Good video acservicetech as usual. I would just add that the two connection spades in the middle of the control is for what we use to call "Sure Start" connections. These connections are on combination controls that were used, in example, down flow furnaces. How it worked was when 24 volt was sent to gas valve on a call for heat, you would see the "w" and" common" at the gas vale sent parallel to these spades connections which was connected to a internal heater to bring the fan on quickly. So in a downflow furnace they were used so the the radiant heat rising up off the heat exchanger and into the fan above it wouldn't damage the blower motor. Hope you don't mind the feedback. Cheers
yeah pre-heater to turn the fan on earlier in down/horizontal flows. without them it may not cycle on for many minutes, overheat badly or trip thermal fuse/secondary limit. they always tripped folks up and ended up cross-wired, so it was common to find burnt gas valves, transformers, thermostats and low voltage wiring with "line voltage".
This is great info because I came across a lennox today that wasn't supplying 24 volts to the gas valve from this combination switch. They should have detailed these two terminals in their video. 5:38
I just had this switch on a Magic Chief furnace 1998… Does it worth now to mess with the switch replacement or 25-years old furnace is ready to be replaced? :)
We just had a Tech come out and troubleshoot our Honeywell controller switch. Without even trying to figure out what the issue is/was he said we have to replace the entire furnace. Is there a replacement for a Honeywell L498B controller?
Can I interchange another unit if it's the same temperature range and length of proe ? I have another , looks the same but I don't know the probe size of one in said furnace .
My fan limit switch keeps cycling the furnace off. Over the summer I removed and cleaned the blower. I also put in a new filter. Just to trouble shoot I removed the filer for max air flow. The fan limit switch rises in temp quickly and shuts the furnace down after a min or two. It cycles again in about 30 sec to a min. I have all the vents wide open. It was working good before I cleaned the blower, lol! any ideas what I should check next? anyway to clean the limit switch rod? have you seen them go bad like this? The blower seemed to be working ok. Thanks for the help!
I have an old Armstrong wood and coal furnace, I want my furnace to kick on more than it does now that it's getting down in the 20s and below, what can I set those on to get the blower to come on more?
Great video! The model you're showing is the Honeywell L4064Y1441, I can't seem to find any direct replacements on it for my York furnace, but a few sites show the L4064B2210 as a replacement but it doesn't have the center 2 spade connectors. Can this L4064B2210 be installed, if so, what to do with the two yellow wires coming from the gas valve that used to connect to the 2 center blade connectors?
You should be able to get it at the local supply house but the two center tabs are for downflow so that the furnace doesn't overheat in the beginning, thanks
So i have a question i have one these on my wood furnace it looks like my dial is screwed up or something It goes way past 50 counterclockwise without a fire and with a fire burning stove is hot to touch and the dial is at 100 if blowers do kick on its just fpr a second you think my switch is screwed up? On my limit side i have .5ohms and an oL on the fan side with the switch dial at 100 if i turn dial a little more to make blowers kick on it reads .1ohms
I have a bad (open) limit switch with fan control on an old ge furnace. If I look for it online by the number it doesn't appear. Is their an option for replacement.
When a limit around 200F is reached, gas turns off, blower is still on. At what temp setting will the gas turn on again? This is for a case when gas pressure is too high coming out from preset factory setting of gas valve and blower works but speed is too low.
Very well detailed video. I have an older Lennox G12Q3-110-4 furnace i'm currently using in my shop. I'm having issues with furnace only blowing on a low speed. I tested the fan limit control switch. I checked continuity on fan (black) wires and always have continuity regardless of me rotating the dial. This is a 110,00 btuh furnace and seems like it should blow harder on "heat". If i turn thermostat to cool and turn fan to "on" it will blow much harder. Would you happen to know if this is the way it should operate? My chamber is only getting to about 110 degrees with low set at 90 and high set at 120. Any help is appreciated, subscribed!
Hello great video!thank you , i have a question my heater doesn't work i have 24 volts from the transformer and as well in i the main board the gas valve opens but no spark after the valve gas opens then it shut down automatically but no spark at all blower only works in on not in automatic ruud furnace same unit control what can possibly be your opinion is highly appreciated thank you again.
@@acservicetechchannel good morning I have a Lenox an the fan won't shut off I check the thermostat its ok I took the bottom door off an fiddled with the switch now it seems to work but if that's not the problem what could it be?
My furnace has a fan limit switch like the one in the video , but my blower fan does not turn off . Tstat is set on auto for fan , I disconnect 24v from tstat R and G and blower is still running . Could it be that the fan limit switch is bad ? Could a clogged filter be the problem as well?
Good Video! Question, Have you ever heard the bimetal in the air stream called a "bonnet"? We have had a code question a couple times now that asks "What causes the blower to start in a heating furnace?" the answer is "the bonnet heats up"...? Just wondering. Thank you,
Our Lennox Pulse G14 only runs properly when the thermostat setting is on "FAN" AND NOT ON "AUTO." (When set on "AUTO," the fan usually does not come on.) Is it okay to run it with the thermostat set on "FAN" all the time? Could this be due to a bad thermostat, or bad Fan Limit Control Switch ? THANK YOU FOR ANY ADVICE !
Is there a way to wire an external switch to control the fan? My furnace is nearly 40 yrs old and the only stand alone fan control is the fan limit switch
Lately my fan limit control switch has been acting up. It is a very old White-Rodgers 5D51-37 with a 5" probe. The problem is: the fan doesn't come on so it reaches the temperature limit after about 4 minutes of the furnace being on, and shuts the furnace off. If I manually turn the dial slightly (counter-clockwise I think), the fan comes on, which cools things down, and about a minute later, the furnace comes back on. It started happening about a couple of weeks ago, and at first, when I "fixed" it by manually by turning the dial slightly, it continued to work fine on its own for about a week. Then I had to fix it again, and it worked fine for a few days, and so on, and now I have to fix it every time the furnace comes on. It seems like a simple device, and the dial can be turned by hand easily enough (it's under spring tension from the coiled bimetal strip in the probe) in both directions, so I can't imagine what the problem is.
I was wondering if there was any way to have the fan on more often / for longer by adjusting the settings. I thought that it was possible but now it seems not because if you have them further apart, the fan stays on longer but it also takes longer for it to come on, similarly if they are closer together, it takes less time for the fan to come on, but also the fan stays on for less time. Overall you get more or less the same fan time as a result. We have a woodwaste heater. Any recommendation specifically for the on off settings in our application? Many thanks.
Really ,really,really suprised you never spoke about the jumper.Thebrass jumper,most likely the last 3 guys that watched this are watching it because they just smoked one.The brass jumper in the center ,you break if your limit is in a 24 v circuit.
When my burners light, about 3-5 seconds later I get a bang sound. It seems to be coming from limit fan switch. I was wondering if the metal elements in the shaft of limit switch is getting hung up when it starts to turn. Everything is working just find, just get that bang sound seconds after the burners light. Thanks for you help. DAVID
I had a lady that sits in front of the heating vent and when the burner shuts down where the fan keeps running toward the end of the heating cycle she feels a gust of cold air coming out until the furnace fan shuts down. The fan limit settings were set at 95/120/200 on oil fired unit.
Then if unplug the cord i have 24.8ohms on fan side and still .3ohms on the limit side what am i hooking up wrong here its hooked up to thermostat but it wont turn blowers on and if i get ot to wprk with the thermostat then the draft/combustion blower wont work
I need a new limit switch for a camper furnace. It's a L170-40F. I see some limit switches online with that description. Would that be the only factor to look for ?
Vary vary good explanation as well !!!! I was going to ask if you could do a video of RIB RELAY Ribu1c. That would be really really appreciated!! Thankyou
Sorry to bother but Can you show me how to wire a CAM STAT SUPCO FALTS combination fan limit control? I retrofitted my old Rheem with a Y8610U universal intermittent pilot ignition kit and I’m not sure on how to wire it so that my limits work. Thanks!
I only have one wire coming in the left side, at the top. There is no wire on the bottom left. My motor runs continuously and I am trying to figure out if this is the issue
Hello thanks for the amazing videos. I was wondering, Is there an easy tell by looking at a blower to tell if it is multi speed or variable speed. Like is multi speed taps as apparently to connection block or something. Also what is the key differences? Thanks in advance. You rock.
I got a question for you. Hope you can help. have one similar.. But it had a push/pull for auto and manual.. I put it on manual(always on) the other day and now it won't switch to auto.. Was wondering if i can bypass the pushpull to have it auto again
@@acservicetechchannel its not locked in place. But when i put it on auto it doesnt stop the blower.. And it should since furnace is off. And blower set to turn on at proper temp. I feel like im doing something wrong. Its very smooth push n pull.. No resistance
Turn the blower off setting to a higher temp position and if it doesn't turn off then the fan limit should be replaced because the settings are not allowing it to shut off.
I have a problem the fan runs all the time with the panel on but it runs backwards. I take the cover off and the fan runs the right way. The-only way to turn it off is to unplug the heater. I need help any ideas
Hello, Excellent video thanks... im troubleshooting my setup which has the same limit switch. however only sometimes, usually when its colder and first thing in the morning the limit switch wont turn the fan on and it goes into overheat. You can watch it rotate past the second 'on' point and just keep going to the limit. Any ideas? many thanks
Hello! Great video! Question: I just replaced the belt drive blower motor with one that is basically the same (1/3 horsepower, 1725RPM, etc..) the problem with the switch above is: that after kicking on the motor at 150F it starts to go backwards until it hits 90F and shuts off. This takes about 5-10 minutes. If I left it like this it would do it forever. Any suggestions? Thanks for any advice. Bryce
Unfortunately you would need a motor with the same directional rotation. The only other way is dismantling the motor and switching the internals the other way. Also, the motor should turn on at 120 not 150, thanks!
@@acservicetechchannel - It turns out that I had some cold air escaping from an exhaust vent for a gas fireplace that I was using temporarily while my blower motor was busted. Once I closed it all was good! Thanks for the reply. I appreciate it!
Great video, I've tested my switch and it checked out good. My furnace fan starts up when it hits 130ish (the second setting notch), then the switch cools down quick within 10 seconds to the 100 mark(the first setting notch) and the fan kicks out. Then it heats up and turns on again then cools to turn fan off. It is cycling like this a few times until the thermostat kicks out at set temperature. Could the switch be faulty at the "by metal"? And would replacing the switch resolve this?
Most likely yes replace it. It could be that the blower speed is too low though if the blower turned on at the right heat but couldn't move the heat fast enough, thanks
Hello again, I swapped out the limit switch a month ago. The hard part was finding a supplier to sell it to me. Everything seems to be working fine now. I did change the settings to 90 to kick out and around 125 to kick in. The fan stays on longer to cool the heat exchanger. Thanks again for your help and saving me a service call.
Im replcing my limit switch today. Im wondering about whether i need to pull the jumper tab on the new one? Its hord to tell if the old one has the jumper or not. Can someone help me?
Hi My furnace shut it self down as the gas valve stop working properly...no heat. The technician who came over determined the valve was at fault. He mentioned that the furnace is 15yrs old and is at it's end of it's life span. This is the first problem we had with the furnace. He seemed to be hinting at replacing the furnace. He called his parts supplier and found out the part was not available and it may take 1-2 weeks to get here. Its winter I need heat. I found the part myself at a different supplier but as I don't have a gas license i couldn't buy the part. I informed him and he got the part for me the next day. He apologized for not checking another source. I question if he was honest about this...Perhaps he was hoping to get me to buy a new furnace instead. However, now it seems I get heat in the first stage, and it takes a long time for the second stage to kick in. When the second stage kicks in it runs for a rather long time blowing cold air before it shuts down. I noticed this about a week and half later. So the house gets warm, then it gets cooled off with cold air blowing. I wonder if he didn't set the limits properly (or on purpose). From what I recall when the second stage kicked in we got a lot of heat and the house warmed up fast. I'm a little hesitant calling the company back. I'm also hesitant to call another company as I'd like to have some kind of idea as to what is really going on and how the furnace properly works. Would the fan limit control need to be adjusted? Thanks
I have an issue! I turn mine to 80 shut off and it goes off the about 30 seconds to a minute later it goes back on for 30 seconds or then off! Thermostat is set at 76 degrees! Switch is new! Why does it do this? Is this dangerous? Thanks Michael
Thermostat shuts off at 76 degrees. Furnace gas shuts off and fan runs till limit switch shuts off at 80 degrees! After it off 30 seconds later the blower goes on for 30. 45. A minute runs about 15 second and shuts off till thermostat turn it back on. Thanks
I wouldn't jump it out but just measure with a multimeter if there is 120v present from common to the tap that says limit. If there is not then the limit is tripped if you do have voltage from the hot at the bottom to common, thanks
The content here is a touchstone. A book I read with similar ideas became a touchstone for my growth. "A Life Unplugged: Reclaiming Reality in a Digital Age" by Theodore Blaze
Absolutely wrong!! The purpose for the 120 degree setting is so the fan does not cycle and blow cold air without heat! It allows a preheat. The purpose of the 90 degree setting is the blower will exact that temperature from the heating chamber before shutting off!...learn your control before you post a sequence of operation!!!
Hey Mack, I said 90 degrees because too many people are trying to squeeze out the little extra efficiency by letting the fan run down to 80 degrees on the first pin to cool the heat exchanger air. What happens over time is the switch tends to get a little off and then the fan limit just continues to run and doesn't shut off. I have had quite a few people asking me about why the fan won't shut off on their furnace. The furnace fan keeps turning out to be controlled by the fan limit instead of a board with the first pin setting too low. The 120 degree second pin is certainly for the heatup before the fan turns on and what better of a fan on setting than the exact temp rise that the furnace is supposed to run at since this is not a timed relay but instead is a temperature controlled relay. I could have put it another way, thanks!
Tool List- www.amazon.com/shop/acservicetech
Support- www.patreon.com/acservicetech
For those that are looking for the tools used in the videos: (Linked Below)
Here is the Link for the newer UEI DL469 Multimeter- amzn.to/2jw4ePJ
Here is a link for the Supco Magnet Jumpers amzn.to/2gS4h6z
Here is the Link for the newer UEI DL479 Multimeter with temp sensor- amzn.to/2jtsUbJ
Here is the link to the 2 pairs of alligator clips- amzn.to/2CtIL5z
Here is the Link for the UEI DL389 Multimeter used in the video - amzn.to/2naJr9o
Here is the Link for the FieldPiece ST4 Dual Temp Meter- amzn.to/2AhR6ph
Here is the Link for the UEI Temp Sensor- amzn.to/2kawAmJ
Here is the link for the Irwin Wire Stripper/Cutter/Crimper- amzn.to/2dGTj2V
Here is a link to the Stanley 6 in 1 screwdriver- amzn.to/2x7NuaZ
Other tool links can be found in the video description section.
ACSERVICETECH is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.
All of the ACSERVICETECH Playlists- th-cam.com/channels/OZR-1IqsAer9wzlvFgb4mA.htmlplaylists?view_as=public
If you want to support the ACSERVICETECH Channel and receive more HVACR content, check out www.Patreon.com/acservicetech
I have bad memory of this switch.
I remember it was copper metal bottom of switch;I did not remove it and damaged the gas valve and thermostat of client.
It was -20 and client was angry and complained me and I lost my job.
Now I am not in HVAC anymore but i love your videos and your videos really helps me to improve my knowledge and someday work for myself.
Please continue.You teach very well.
Thank you very much! it's really nice to see explanation videos on the older technology. I honestly find older furnaces harder to diagnose because I didn't grow up servicing them. So to see in depth explanations on what some may feel is a really simple component is advantageous to technicians that were taught mostly newer tech.
Thanks Mitch!
Hi, Thank you for the awesome video. Sometimes changing the thermostat can save you 5k to 10k on this HVAC system (lol).
"HVAC CAN BE DANGEROUS; DO NOT ATTEMPT ANY REPAIR IF YOU HAVE NO KNOWLEDGE OF WHAT YOU ARE DOING."
I have an old furnace in my house. I had the relay buzzing very loudly inside the furnace. Called the technician he said it was the transformer and relay, and would charge $300 for the relay only (lol). He also advised me to put a new and more efficient HVAC system. Called another one he also told me your system is old get a new one. He told me your furnace and AC are running at the same time (bu**). After he left, I checked the outside unit wasn't running.
After that, I decided to take matters into my own hand. I made my own wiring diagram of the furnace system since the older system is simple without any circuit boards. Checked voltage on the transformer, limit switch, relays, and so on. While checking the voltage on the relay coil (magnetize switch ) and it was 3 V instead of 24 V. Since I had the wiring diagram ready I figured out the culprit was a thermostat. I also had to replace thermostat batteries twice that week but it was hard to relate it with relay buzzing since I had no idea of the system before. I replaced the thermostat with a new one since it was in warranty. I am using the smart google Nests thermostat. It took me 3 days to do the above tasks.
So in summary, I saved myself 5k to 10 k for the new HVAC system.
Good luck with your diagnostics everyone.
Thanks!!! Just fixed my furnace thanks to this
Good video acservicetech as usual.
I would just add that the two connection spades in the middle of the control is for what we use to call "Sure Start" connections. These connections are on combination controls that were used, in example, down flow furnaces. How it worked was when 24 volt was sent to gas valve on a call for heat, you would see the "w" and" common" at the gas vale sent parallel to these spades connections which was connected to a internal heater to bring the fan on quickly. So in a downflow furnace they were used so the the radiant heat rising up off the heat exchanger and into the fan above it wouldn't damage the blower motor.
Hope you don't mind the feedback.
Cheers
I appreciate your input very much Paul!
yeah pre-heater to turn the fan on earlier in down/horizontal flows. without them it may not cycle on for many minutes, overheat badly or trip thermal fuse/secondary limit.
they always tripped folks up and ended up cross-wired, so it was common to find burnt gas valves, transformers, thermostats and low voltage wiring with "line voltage".
Thanks a lot Throttle Bottle!
This is great info because I came across a lennox today that wasn't supplying 24 volts to the gas valve from this combination switch.
They should have detailed these two terminals in their video. 5:38
Great video helps me to learn about fan control limit switch. I need to open my furnace to locate and see where this thing is.
This was great! Thanks for sharing.
Hey thanks for the info, appreciate your work brother!
Any time!
Very clear great explanation, thank you!
Great explanation! I always enjoy your videos. Thanks for sharing!!
Thanks Johnny!
Its neat that this thing can simply be turned to test the switches.
How do you test the thermal switch located on the blower cage?
Keep the videos coming! Great content!!!
Thank you so much for the video. But the previous tech missed up all the wires. Would have been great if there was mention which is 24v and 120v
I’m running into this exact problem now ☹️
@marcelinomagana5336 grayfurnaceman have a video on this.
This is a very informative video. Thanks for putting it together.
Thanks Michael!
I just had this switch on a Magic Chief furnace 1998… Does it worth now to mess with the switch replacement or 25-years old furnace is ready to be replaced? :)
We just had a Tech come out and troubleshoot our Honeywell controller switch. Without even trying to figure out what the issue is/was he said we have to replace the entire furnace. Is there a replacement for a Honeywell L498B controller?
Good stuff, thanks
As Always very informative.
Thanks Channel Cat Chaser!
Can I interchange another unit if it's the same temperature range and length of proe ? I have another , looks the same but I don't know the probe size of one in said furnace .
My fan limit switch keeps cycling the furnace off. Over the summer I removed and cleaned the blower. I also put in a new filter. Just to trouble shoot I removed the filer for max air flow. The fan limit switch rises in temp quickly and shuts the furnace down after a min or two. It cycles again in about 30 sec to a min. I have all the vents wide open. It was working good before I cleaned the blower, lol! any ideas what I should check next? anyway to clean the limit switch rod? have you seen them go bad like this? The blower seemed to be working ok. Thanks for the help!
And 5 minutes later I understand how this works!!!!!!!
Thanks Douglas!
There appears to be to male spade connectors in the center of the unit (just below the dial), what are they for? Mine has yellow wires attached.
I have an old Armstrong wood and coal furnace, I want my furnace to kick on more than it does now that it's getting down in the 20s and below, what can I set those on to get the blower to come on more?
Which ports have power ??
Great video! The model you're showing is the Honeywell L4064Y1441, I can't seem to find any direct replacements on it for my York furnace, but a few sites show the L4064B2210 as a replacement but it doesn't have the center 2 spade connectors. Can this L4064B2210 be installed, if so, what to do with the two yellow wires coming from the gas valve that used to connect to the 2 center blade connectors?
You should be able to get it at the local supply house but the two center tabs are for downflow so that the furnace doesn't overheat in the beginning, thanks
So i have a question i have one these on my wood furnace it looks like my dial is screwed up or something It goes way past 50 counterclockwise without a fire and with a fire burning stove is hot to touch and the dial is at 100 if blowers do kick on its just fpr a second you think my switch is screwed up? On my limit side i have .5ohms and an oL on the fan side with the switch dial at 100 if i turn dial a little more to make blowers kick on it reads .1ohms
I have a bad (open) limit switch with fan control on an old ge furnace. If I look for it online by the number it doesn't appear. Is their an option for replacement.
When a limit around 200F is reached, gas turns off, blower is still on. At what temp setting will the gas turn on again?
This is for a case when gas pressure is too high coming out from preset factory setting of gas valve and blower works but speed is too low.
What's the two spade terminals in the middle. Is that a secondary kill
Read the comments
Very well detailed video. I have an older Lennox G12Q3-110-4 furnace i'm currently using in my shop. I'm having issues with furnace only blowing on a low speed. I tested the fan limit control switch. I checked continuity on fan (black) wires and always have continuity regardless of me rotating the dial. This is a 110,00 btuh furnace and seems like it should blow harder on "heat". If i turn thermostat to cool and turn fan to "on" it will blow much harder. Would you happen to know if this is the way it should operate? My chamber is only getting to about 110 degrees with low set at 90 and high set at 120. Any help is appreciated, subscribed!
Hello great video!thank you , i have a question my heater doesn't work i have 24 volts from the transformer and as well in i the main board the gas valve opens but no spark after the valve gas opens then it shut down automatically but no spark at all blower only works in on not in automatic ruud furnace same unit control what can possibly be your opinion is highly appreciated thank you again.
Is there anything you can do if you can get the fan to stop blowing ? It's the weekend and can't get parts .
Do you have part number for limit switch shown ?
As always,good job
Thanks mpflood!
@@acservicetechchannel good morning I have a Lenox an the fan won't shut off I check the thermostat its ok I took the bottom door off an fiddled with the switch now it seems to work but if that's not the problem what could it be?
Hey! Does the fan stay on constantly during the whole heating cycle with this control?
My furnace has a fan limit switch like the one in the video , but my blower fan does not turn off . Tstat is set on auto for fan , I disconnect 24v from tstat R and G and blower is still running . Could it be that the fan limit switch is bad ? Could a clogged filter be the problem as well?
Hey brother can you tell me what is the function of the 2 middle taps in the dial limit switch most new ones don’t have those taps ?
Good Video!
Question, Have you ever heard the bimetal in the air stream called a "bonnet"? We have had a code question a couple times now that asks "What causes the blower to start in a heating furnace?" the answer is "the bonnet heats up"...?
Just wondering.
Thank you,
Our Lennox Pulse G14 only runs properly when the thermostat setting is on "FAN" AND NOT ON "AUTO." (When set on "AUTO," the fan usually does not come on.) Is it okay to run it with the thermostat set on "FAN" all the time?
Could this be due to a bad thermostat, or bad Fan Limit Control Switch ? THANK YOU FOR ANY ADVICE !
Is there a way to wire an external switch to control the fan? My furnace is nearly 40 yrs old and the only stand alone fan control is the fan limit switch
Lately my fan limit control switch has been acting up. It is a very old White-Rodgers 5D51-37 with a 5" probe. The problem is: the fan doesn't come on so it reaches the temperature limit after about 4 minutes of the furnace being on, and shuts the furnace off. If I manually turn the dial slightly (counter-clockwise I think), the fan comes on, which cools things down, and about a minute later, the furnace comes back on.
It started happening about a couple of weeks ago, and at first, when I "fixed" it by manually by turning the dial slightly, it continued to work fine on its own for about a week. Then I had to fix it again, and it worked fine for a few days, and so on, and now I have to fix it every time the furnace comes on. It seems like a simple device, and the dial can be turned by hand easily enough (it's under spring tension from the coiled bimetal strip in the probe) in both directions, so I can't imagine what the problem is.
They go bad. The bimetal is rubbing on the outer metal likely but that part needs to be replaced, thanks
Would this be typical on a wood furnace.... IE on at 120 -130 and off at say 90?
I was wondering if there was any way to have the fan on more often / for longer by adjusting the settings.
I thought that it was possible but now it seems not because if you have them further apart, the fan stays on longer but it also takes longer for it to come on, similarly if they are closer together, it takes less time for the fan to come on, but also the fan stays on for less time.
Overall you get more or less the same fan time as a result.
We have a woodwaste heater. Any recommendation specifically for the on off settings in our application?
Many thanks.
What model of limit control switch is that you are showing?
Really ,really,really suprised you never spoke about the jumper.Thebrass jumper,most likely the last 3 guys that watched this are watching it because they just smoked one.The brass jumper in the center ,you break if your limit is in a 24 v circuit.
Thanks!
When my burners light, about 3-5 seconds later I get a bang sound. It seems to be coming from limit fan switch. I was wondering if the metal elements in the shaft of limit switch is getting hung up when it starts to turn. Everything is working just find, just get that bang sound seconds after the burners light. Thanks for you help. DAVID
Sounds more like dirty burners or something
I had a lady that sits in front of the heating vent and when the burner shuts down where the fan keeps running toward the end of the heating cycle she feels a gust of cold air coming out until the furnace fan shuts down. The fan limit settings were set at 95/120/200 on oil fired unit.
Thanks
What do you do when you run into 1 that turns gas on and off while fan is running change it ? Thanks
Then if unplug the cord i have 24.8ohms on fan side and still .3ohms on the limit side what am i hooking up wrong here its hooked up to thermostat but it wont turn blowers on and if i get ot to wprk with the thermostat then the draft/combustion blower wont work
I need a new limit switch for a camper furnace. It's a L170-40F. I see some limit switches online with that description. Would that be the only factor to look for ?
Yes but also how the sensor is mounted. Make sure the mount is the same, thanks and sorry for getting back to you late!
If you want to support each new video on the ACSERVICETECH Channel and get rewarded with more HVACR content, check out www.Patreon.com/acservicetech
My oil furnace heats up turns off then comes back on a minute later for 30 seconds or so. Would this be the cause if its defective?
Do you know the part # for this control unit
This is the exact limit switch we need to replace but we can't find it anywhere, does anyone know the part number for this exact one?
Vary vary good explanation as well !!!!
I was going to ask if you could do a video of RIB RELAY Ribu1c.
That would be really really appreciated!!
Thankyou
Gentian, thanks for letting me know what you would like to see!
Would this be typical on a wood furnace as well? IE on at 120-130 and off at 90?
Yes, thats how mine is..
Sorry to bother but Can you show me how to wire a CAM STAT SUPCO FALTS combination fan limit control? I retrofitted my old Rheem with a Y8610U universal intermittent pilot ignition kit and I’m not sure on how to wire it so that my limits work. Thanks!
I only have one wire coming in the left side, at the top. There is no wire on the bottom left. My motor runs continuously and I am trying to figure out if this is the issue
You would need to have a second wire for the voltage to go anyway, thanks
How do you move those little knobs 1 2 and 3 ?? With a screwdriver?
Hello thanks for the amazing videos. I was wondering, Is there an easy tell by looking at a blower to tell if it is multi speed or variable speed. Like is multi speed taps as apparently to connection block or something. Also what is the key differences? Thanks in advance. You rock.
Thanks Daniel! Did you see this video?- th-cam.com/video/EHwTZFvv-2Q/w-d-xo.html
acservicetech perfect you cover everything so well man keep it up.
I got a question for you. Hope you can help. have one similar.. But it had a push/pull for auto and manual.. I put it on manual(always on) the other day and now it won't switch to auto.. Was wondering if i can bypass the pushpull to have it auto again
Usually the push/pull will go back in. It shouldn't lock into place unless the contacts melted together due to amperage, thanks
@@acservicetechchannel its not locked in place. But when i put it on auto it doesnt stop the blower.. And it should since furnace is off. And blower set to turn on at proper temp.
I feel like im doing something wrong. Its very smooth push n pull.. No resistance
Turn the blower off setting to a higher temp position and if it doesn't turn off then the fan limit should be replaced because the settings are not allowing it to shut off.
@@acservicetechchannel thanks for the tip, will give it a go tomorrow
I have a problem the fan runs all the time with the panel on but it runs backwards. I take the cover off and the fan runs the right way. The-only way to turn it off is to unplug the heater. I need help any ideas
Hello,
Excellent video thanks... im troubleshooting my setup which has the same limit switch. however only sometimes, usually when its colder and first thing in the morning the limit switch wont turn the fan on and it goes into overheat. You can watch it rotate past the second 'on' point and just keep going to the limit. Any ideas? many thanks
That sounds like you should replace the limit as it is out of parameters for temp or the contacts are bad, thanks
acservicetech great thanks
Hello! Great video! Question: I just replaced the belt drive blower motor with one that is basically the same (1/3 horsepower, 1725RPM, etc..) the problem with the switch above is: that after kicking on the motor at 150F it starts to go backwards until it hits 90F and shuts off. This takes about 5-10 minutes. If I left it like this it would do it forever. Any suggestions? Thanks for any advice. Bryce
Unfortunately you would need a motor with the same directional rotation. The only other way is dismantling the motor and switching the internals the other way. Also, the motor should turn on at 120 not 150, thanks!
@@acservicetechchannel - It turns out that I had some cold air escaping from an exhaust vent for a gas fireplace that I was using temporarily while my blower motor was busted. Once I closed it all was good! Thanks for the reply. I appreciate it!
OL means “open loop”. In the Northeast that’s what it means.
Great video, I've tested my switch and it checked out good. My furnace fan starts up when it hits 130ish (the second setting notch), then the switch cools down quick within 10 seconds to the 100 mark(the first setting notch) and the fan kicks out. Then it heats up and turns on again then cools to turn fan off. It is cycling like this a few times until the thermostat kicks out at set temperature. Could the switch be faulty at the "by metal"? And would replacing the switch resolve this?
Most likely yes replace it. It could be that the blower speed is too low though if the blower turned on at the right heat but couldn't move the heat fast enough, thanks
Hello again, I swapped out the limit switch a month ago. The hard part was finding a supplier to sell it to me. Everything seems to be working fine now. I did change the settings to 90 to kick out and around 125 to kick in. The fan stays on longer to cool the heat exchanger. Thanks again for your help and saving me a service call.
glad to help!
Im replcing my limit switch today. Im wondering about whether i need to pull the jumper tab on the new one? Its hord to tell if the old one has the jumper or not. Can someone help me?
Hi My furnace shut it self down as the gas valve stop working properly...no heat. The technician who came over determined the valve was at fault. He mentioned that the furnace is 15yrs old and is at it's end of it's life span. This is the first problem we had with the furnace. He seemed to be hinting at replacing the furnace. He called his parts supplier and found out the part was not available and it may take 1-2 weeks to get here. Its winter I need heat. I found the part myself at a different supplier but as I don't have a gas license i couldn't buy the part. I informed him and he got the part for me the next day. He apologized for not checking another source. I question if he was honest about this...Perhaps he was hoping to get me to buy a new furnace instead. However, now it seems I get heat in the first stage, and it takes a long time for the second stage to kick in. When the second stage kicks in it runs for a rather long time blowing cold air before it shuts down. I noticed this about a week and half later. So the house gets warm, then it gets cooled off with cold air blowing. I wonder if he didn't set the limits properly (or on purpose). From what I recall when the second stage kicked in we got a lot of heat and the house warmed up fast. I'm a little hesitant calling the company back. I'm also hesitant to call another company as I'd like to have some kind of idea as to what is really going on and how the furnace properly works. Would the fan limit control need to be adjusted? Thanks
I have an issue! I turn mine to 80 shut off and it goes off the about 30 seconds to a minute later it goes back on for 30 seconds or then off! Thermostat is set at 76 degrees! Switch is new! Why does it do this? Is this dangerous? Thanks Michael
Are you saying you are turning your thermostat to 80 and what is going off and one, heat or blower motor?
Thermostat shuts off at 76 degrees. Furnace gas shuts off and fan runs till limit switch shuts off at 80 degrees! After it off 30 seconds later the blower goes on for 30. 45. A minute runs about 15 second and shuts off till thermostat turn it back on. Thanks
hi , im a new tech, , is there any way i can by pass this limit switch
I wouldn't jump it out but just measure with a multimeter if there is 120v present from common to the tap that says limit. If there is not then the limit is tripped if you do have voltage from the hot at the bottom to common, thanks
The content here is a touchstone. A book I read with similar ideas became a touchstone for my growth. "A Life Unplugged: Reclaiming Reality in a Digital Age" by Theodore Blaze
Sir t6373b1130 honeywell thermostat wiring Ac video
Thanks for letting me know what you would like to see!
I don’t have this in my furnace
You likely have a control board then. You could look up "acservicetech blower motor" for videos on blower controls, thanks
Bro, decent job an all.. but O.L. DEFINITELY doesn't mean "over limit" 🤣 it mean OPEN LOOP.
Over limit means over the limit of resistance that the meter can read. Open line, Over Limit, Open Limit all mean the same thing, thanks
Absolutely wrong!! The purpose for the 120 degree setting is so the fan does not cycle and blow cold air without heat! It allows a preheat. The purpose of the 90 degree setting is the blower will exact that temperature from the heating chamber before shutting off!...learn your control before you post a sequence of operation!!!
Hey Mack, I said 90 degrees because too many people are trying to squeeze out the little extra efficiency by letting the fan run down to 80 degrees on the first pin to cool the heat exchanger air. What happens over time is the switch tends to get a little off and then the fan limit just continues to run and doesn't shut off. I have had quite a few people asking me about why the fan won't shut off on their furnace. The furnace fan keeps turning out to be controlled by the fan limit instead of a board with the first pin setting too low. The 120 degree second pin is certainly for the heatup before the fan turns on and what better of a fan on setting than the exact temp rise that the furnace is supposed to run at since this is not a timed relay but instead is a temperature controlled relay. I could have put it another way, thanks!
I back most of them down to 100F on and 80F off and limit the temp to 160F. poor mans efficiency, with air still warmer than most 90+
Sorry - u lost me with your first words...
No good explanation