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 Yellow Jacket Refrigerant Manifold Gauge Set used in the videos- amzn.to/2aenwTq Here is a link to Refrigerant hoses with valves used in the videos- amzn.to/2aBumVI Here is a link to the UEI DL389 Multimeter used in the videos- amzn.to/2av8s3q Here is a link to the Hilmor 4 port Aluminum Manifold Gauge Set- amzn.to/2m4QLik Here is a link to the Digital Refrigerant Scale used in the videos- amzn.to/2b9oXYl 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.com.
Just had this exact problem with mine. I don't know much about HVAC systems but I do know a lot about electric motors and electronics, so I just applied that knowledge to troubleshooting the furnace. The motor started just humming and wouldn't start, so I changed the capacitor and the flame sensor. It still didn't work and was getting a bad burning smell, so I assumed the windings burned out. I removed the motor, planning on looking for a new one but after about an hour of searching online for a new motor, I decided to try one last thing. I cut the ends off of a power cord, wired the motor up in my living room, connected the common and then went through the different speeds and to my surprise they all worked. I did not expect the motor to turn over at all since I had come to the conclusion that it was fried. I had a closer look and noticed it had 2 thermal fuses and then realized that I just hadn't given it enough time to cool down before so the fuses would reset. I reinstalled the motor and is running just fine now, so far😬 I was so so close to chucking out that motor and spending $150 on a new motor that I didn't need.
Exactly and knowledge may get worse and worse depending on how it gets passed down. Yes a lot has changed because we cannot simply change out parts until the problem goes away. Manufacturers and distributors now actually penalize those that warranty parts in this way. Most manufacturers say that they test all of the so called bad components coming back.
Great video! I understand that one of the brown capacitor wires connects to the start winding, where does the other brown wire connect inside of the motor?
For a bad motor a simple check if it’s shorted to ground is that also a good check to determine if it’s a bad motor. I usually check to resistance between one of the windings and the blower squirrel cage. Bad motors are usually grounded.
This is a good tutorial. I have a Coleman single stage furnace that ran great after changing the pressure switch. Shut the unit off and on several times and worked good. Next morning I get a call for no start. Reset on off switch at furnace, worked great no problems. Get a call following morning for same issue. I pop the capacitor off at the blower wheel, and checked farads. Should be at 7.5 and it’s at 6.1. Replace capacitor, unit runs stronger, and flames seem to be stronger too. Get call following morning. So I’m assuming I should check resistance now at all wires?
Nice but i had to pull up a wiring diagram of a PSC motor to fully get the picture. I think others would also benefit from a wiring schematic. Thanks for great video
nope, thank you, we have been in the industry for a while now and its always a good thing to come back and stay fresh and informed. very much like your post thanks again.
Hello! Great explanation! So, if i bridge the connections between the thermal fuse for testing the motor should be okay? The motor start to get very hot in the coils when connect to AC. It kind of shorting?
In my blower motor, there is no resistance between common wire and speed's wires. Same thing between capacitor's wires, without the capacitor. What should I test ?
Concerning the different speeds, are the colored wires (not including common) themselves the ones that are providing the different resistance values and thereby the different speeds? Or is there something else that is unique about the motor windings? Thanks!
Yes each winding is actually a different length and each resistance is shown by the color which would indicate the speed. The higher the resistance value between this wire and the common the slower the fan speed, thanks
I have an 3 speed blower motor. It would run for a 2-3 minutes then stop running while there are still 277v going to it. I tested the capacitor and it’s good. It look like the thermal overload trip. Any advise? FYI the motor is new.
Thank you so much for responding. The voltage is correct 277v and motor is also 277v rating. The capacitor is 4 uf and that’s what it also said on the motor also. That only cause I can think of right now is the thermal overload keep tripping. If I shut off the vav and turn it back on the next day it would run for 2-3 minute. However if I turn it off then it turn it back on right away it’s would only run for 20-30 second, maybe it not enough time for the overload to cool down? Also the original capacitor that was install is 7.5 uf before I change it out for the correct 4uf capacitor, so I’m not sure if the 7.5uf capacitor already did some damage before I put in the correct capacitor. Thank you
So I measured both brown wires, which are the start and run windings. I got continuity and a resistance of 8.6 ohms. I then started to move the shaft around and it went up to 46.3 ohms and stayed there with no continuity, is this normal? Shaft turns freely and everything else checks out ok. But when line voltage is applied it only hums. Thanks
Usually when measuring the resistance readings of the capacitor wires, they are a much higher resistance reading then any of the speed wires. Bottom line is if you have a good capacitor and you have good inlet voltage and the motor hums then replace the motor, thanks
Hey Floyd, I was just showing that the resistance values on the start winding going to the cap are alot higher than the speed wire resistances to common. This resistance reading will change if it is 240v or a different hp blower motor. I was giving rough readings to look for on 120v 1/2hp motors. Thanks!
acservicetech ah, thank you. So a coil has two separate parts then? Two wires(common and hot leg) that go to two separate parts of the coils and creates electromagnetism? I would assume since you mentioned that they short together implying there’s two separate parts.
Think about one length of wire and the middle is all coiled up. The insulation around the wire is just a clear resin. Since the wire is a very small diameter gauge and so long it has resistance to electrical flow read in ohms with a multimeter when not powered. If the wire resin melts and the coil is not touching all together then it is now not a long wire but a short wire which makes there be less resistance read at close to 0.0 ohms, thanks
acservicetech thanks! Makes sense. Since most of Hvac units deal with AC voltage, I’m trying to understand the concept of ohms, resistance on coils. Any suggestions on what book or videos to research would be greatly appreciated. Thank you again for responding
hey partner I had a tech question to ask you my aunt had a split system installed crappy job lennox 3 ton with a coleman furnace with two air filters that cover the whole front of the furnace no return's all supply's from old unit and is loud as a train at start up! she purchased it at Costco you know how they swindle you in and have some contractor get a guy to do the job any suggestion's to quiet it down? thank's acservicetech...
You could replace the blower with an Evergreen ECM for PSC Blower Motor Replacement possibly. Either this or build another closet frame and another louvered door in front of it, ha. They are just very noisy.
The other thing is that these types of furnaces are mainly only used in mobile homes and if you add an ecm to try to push air through that small 14 x 14 trunk duct it will be very noisy and possibly hurt the blower motor due to high friction as seen through the motor as amperage
thank you acservicetech you are a very smart tech I respect you highly!!! I did not even mention to you that it was a mobile home which is now considered a home because she had a foundation added, wow so she is basically stuck with that loud furnace, thanks a million for your help you are a crystal ball!!!
I've watched all of your videos on this topic (I think) and don't see the problem that I'm facing. I'm looking at a Rheem package unit (RRPL 5 ton) that doesn't seem to have a capacitor for the fan...at least one not located near the blower. There is a capacitor near the board and it checks out okay. I was expecting one closer to the blower, however. Also, the motor has male connectors instead of wires coming out. Would I pull the wires and test the male tabs from the motor for resistance? Thanks so much!
+acservicetech I'll check it out. The odd thing with this blower is it does kick on briefly and then shuts down...most of the time. It may run for a minute or so or only 10 to 15 seconds.
I have a single speed blower motor that intermittently decides not to work, no humming. Sits for a day or so and lo and behold it’ll work again for a few days. Based on what this video tells me It shouldn’t be a burnt motor getting hot and tripping the overload, because it will work just fine when it wants to. Should I focus on the cap or TDR?
If it's not humming, it sounds like it's the internal overload. After it stops, i would turn the power off and disconnect the motor wires to test resistance value to see if the common is open, thanks!
After I replaced the run/start cap, and the fan still wouldn't kick on, I measured 2 motor wire legs in the KiloOhm range, and the 3rd leg in the MegaOhm range. Opened up the motor but could not find an overload fuse...maybe covered by the resin? Anyway the motor is 25 years old, so I'm looking for a cheap as possible replacement. It's out of an old Goodman unit. (Next year I'm getting a ductless system).
Yes the thermal overload is covered by the resin and tape right on top of the winding. Sounds like you will need a new psc blower motor. They are not very expensive, 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 Yellow Jacket Refrigerant Manifold Gauge Set used in the videos-
amzn.to/2aenwTq
Here is a link to Refrigerant hoses with valves used in the videos- amzn.to/2aBumVI
Here is a link to the UEI DL389 Multimeter used in the videos- amzn.to/2av8s3q
Here is a link to the Hilmor 4 port Aluminum Manifold Gauge Set-
amzn.to/2m4QLik
Here is a link to the Digital Refrigerant Scale used in the videos-
amzn.to/2b9oXYl
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.com.
AC Service Tech LLC thanks for sending me to this vid. So much awesome info
Mans is doing more for me than my trade school. Thank you so much.
Just had this exact problem with mine. I don't know much about HVAC systems but I do know a lot about electric motors and electronics, so I just applied that knowledge to troubleshooting the furnace. The motor started just humming and wouldn't start, so I changed the capacitor and the flame sensor. It still didn't work and was getting a bad burning smell, so I assumed the windings burned out. I removed the motor, planning on looking for a new one but after about an hour of searching online for a new motor, I decided to try one last thing. I cut the ends off of a power cord, wired the motor up in my living room, connected the common and then went through the different speeds and to my surprise they all worked. I did not expect the motor to turn over at all since I had come to the conclusion that it was fried. I had a closer look and noticed it had 2 thermal fuses and then realized that I just hadn't given it enough time to cool down before so the fuses would reset. I reinstalled the motor and is running just fine now, so far😬 I was so so close to chucking out that motor and spending $150 on a new motor that I didn't need.
Never saw the actual thermal overload until now. Great explanation, too, Craig!
Thanks Jack!
Wow, very insightful! This is stuff that I touch all the time and can now think more about.
great video. Some technicians do not know and are too embarrassed to ask for help
Exactly and knowledge may get worse and worse depending on how it gets passed down. Yes a lot has changed because we cannot simply change out parts until the problem goes away. Manufacturers and distributors now actually penalize those that warranty parts in this way. Most manufacturers say that they test all of the so called bad components coming back.
acservicetech tech are doing sabotage before they turn in the part for warranty
Ha, oh man.
Great video! I understand that one of the brown capacitor wires connects to the start winding, where does the other brown wire connect inside of the motor?
The common
Really appreciated the video and help solve my issue keep doing what your doing
Thanks, will do!
For a bad motor a simple check if it’s shorted to ground is that also a good check to determine if it’s a bad motor. I usually check to resistance between one of the windings and the blower squirrel cage. Bad motors are usually grounded.
Absolutely, thanks
This is a good tutorial. I have a Coleman single stage furnace that ran great after changing the pressure switch. Shut the unit off and on several times and worked good. Next morning I get a call for no start. Reset on off switch at furnace, worked great no problems. Get a call following morning for same issue. I pop the capacitor off at the blower wheel, and checked farads. Should be at 7.5 and it’s at 6.1. Replace capacitor, unit runs stronger, and flames seem to be stronger too. Get call following morning. So I’m assuming I should check resistance now at all wires?
Is it easy to replace the thermo overload? Also how do you know which one you need for your blower?
Nice but i had to pull up a wiring diagram of a PSC motor to fully get the picture. I think others would also benefit from a wiring schematic. Thanks for great video
very cool, I have never seen a thermo overload
Thanks Felipe!
nope, thank you, we have been in the industry for a while now and its always a good thing to come back and stay fresh and informed. very much like your post thanks again.
Hello! Great explanation! So, if i bridge the connections between the thermal fuse for testing the motor should be okay? The motor start to get very hot in the coils when connect to AC. It kind of shorting?
you should have used a megohmeter before and after the thermal cutout to show also, excellant video
Yeah, that would have been good as well, Thanks.
Awesome explanation!
Thanks Sergio!
Should you have resistance between speeds
Very nice, as always
Thanks!
In my blower motor, there is no resistance between common wire and speed's wires. Same thing between capacitor's wires, without the capacitor. What should I test ?
If the motor is cool then the windings are open and the motor will need to be replaced, thanks!
I thought you would test for short from the windings to the body?
Concerning the different speeds, are the colored wires (not including common) themselves the ones that are providing the different resistance values and thereby the different speeds? Or is there something else that is unique about the motor windings? Thanks!
Yes each winding is actually a different length and each resistance is shown by the color which would indicate the speed. The higher the resistance value between this wire and the common the slower the fan speed, thanks
Another gem!
Thanks Brian!
When connecting the brown wires to the capacitor , does it matter which wire goes to which connector ?
Not on a single run cap. Only a dual does it matter, C= common, F= fan, Herm= compressor
very practical, thank you ...
Thanks pei broker!
so will the motor hum if on overload or only hum when bad capacitor
The motor will hum before the overload trips and after the cap fails. Thanks
I have an 3 speed blower motor. It would run for a 2-3 minutes then stop running while there are still 277v going to it. I tested the capacitor and it’s good. It look like the thermal overload trip. Any advise? FYI the motor is new.
Mui, does the rating late say it can be used with 277v? Is the capacitor the correct size as stated on the motor rating plate? Thanks!
Thank you so much for responding. The voltage is correct 277v and motor is also 277v rating. The capacitor is 4 uf and that’s what it also said on the motor also. That only cause I can think of right now is the thermal overload keep tripping. If I shut off the vav and turn it back on the next day it would run for 2-3 minute. However if I turn it off then it turn it back on right away it’s would only run for 20-30 second, maybe it not enough time for the overload to cool down? Also the original capacitor that was install is 7.5 uf before I change it out for the correct 4uf capacitor, so I’m not sure if the 7.5uf capacitor already did some damage before I put in the correct capacitor.
Thank you
great video! Thank you
Thanks for the comment!
So I measured both brown wires, which are the start and run windings. I got continuity and a resistance of 8.6 ohms. I then started to move the shaft around and it went up to 46.3 ohms and stayed there with no continuity, is this normal? Shaft turns freely and everything else checks out ok. But when line voltage is applied it only hums. Thanks
Usually when measuring the resistance readings of the capacitor wires, they are a much higher resistance reading then any of the speed wires. Bottom line is if you have a good capacitor and you have good inlet voltage and the motor hums then replace the motor, thanks
im confused on the wires for the capacitor. so the ohms reading supposed to 20's are 48-50 ohms
Hey Floyd, I was just showing that the resistance values on the start winding going to the cap are alot higher than the speed wire resistances to common. This resistance reading will change if it is 240v or a different hp blower motor. I was giving rough readings to look for on 120v 1/2hp motors. Thanks!
@@acservicetechchannel should the start windings be shorted/ 0 ohms to any of the fan speed wires?
great instructions tutorial, it would be a lot better with the camera focus closer
Thanks for letting me know Young!
What if you got 0.0 for resistance from common to black wire? What would that mean? Thanks
That would mean that the windings are shorted together and the motor should pop the breaker when powered.
acservicetech ah, thank you. So a coil has two separate parts then? Two wires(common and hot leg) that go to two separate parts of the coils and creates electromagnetism? I would assume since you mentioned that they short together implying there’s two separate parts.
Think about one length of wire and the middle is all coiled up. The insulation around the wire is just a clear resin. Since the wire is a very small diameter gauge and so long it has resistance to electrical flow read in ohms with a multimeter when not powered. If the wire resin melts and the coil is not touching all together then it is now not a long wire but a short wire which makes there be less resistance read at close to 0.0 ohms, thanks
acservicetech thanks! Makes sense. Since most of Hvac units deal with AC voltage, I’m trying to understand the concept of ohms, resistance on coils. Any suggestions on what book or videos to research would be greatly appreciated. Thank you again for responding
Very nice video.
Thanks DC Rickerson!
hey partner I had a tech question to ask you my aunt had a split system installed crappy job lennox 3 ton with a coleman furnace with two air filters that cover the whole front of the furnace no return's all supply's from old unit and is loud as a train at start up! she purchased it at Costco you know how they swindle you in and have some contractor get a guy to do the job any suggestion's to quiet it down? thank's acservicetech...
You could replace the blower with an Evergreen ECM for PSC Blower Motor Replacement possibly. Either this or build another closet frame and another louvered door in front of it, ha. They are just very noisy.
The other thing is that these types of furnaces are mainly only used in mobile homes and if you add an ecm to try to push air through that small 14 x 14 trunk duct it will be very noisy and possibly hurt the blower motor due to high friction as seen through the motor as amperage
thank you acservicetech you are a very smart tech I respect you highly!!! I did not even mention to you that it was a mobile home which is now considered a home because she had a foundation added, wow so she is basically stuck with that loud furnace, thanks a million for your help you are a crystal ball!!!
How do you wire the motor out of circuit
I've watched all of your videos on this topic (I think) and don't see the problem that I'm facing. I'm looking at a Rheem package unit (RRPL 5 ton) that doesn't seem to have a capacitor for the fan...at least one not located near the blower. There is a capacitor near the board and it checks out okay. I was expecting one closer to the blower, however. Also, the motor has male connectors instead of wires coming out. Would I pull the wires and test the male tabs from the motor for resistance? Thanks so much!
That sounds like it may be an x13 if it has male spade terminals. Check this video out- th-cam.com/video/ZzvhtmQTiMY/w-d-xo.html
+acservicetech I'll check it out. The odd thing with this blower is it does kick on briefly and then shuts down...most of the time. It may run for a minute or so or only 10 to 15 seconds.
+acservicetech Could this be a loose connection somewhere or is something limiting out on the fan? There is no standing water anywhere that I recall.
I have a single speed blower motor that intermittently decides not to work, no humming. Sits for a day or so and lo and behold it’ll work again for a few days. Based on what this video tells me It shouldn’t be a burnt motor getting hot and tripping the overload, because it will work just fine when it wants to. Should I focus on the cap or TDR?
If it's not humming, it sounds like it's the internal overload. After it stops, i would turn the power off and disconnect the motor wires to test resistance value to see if the common is open, thanks!
After I replaced the run/start cap, and the fan still wouldn't kick on, I measured 2 motor wire legs in the KiloOhm range, and the 3rd leg in the MegaOhm range. Opened up the motor but could not find an overload fuse...maybe covered by the resin? Anyway the motor is 25 years old, so I'm looking for a cheap as possible replacement. It's out of an old Goodman unit. (Next year I'm getting a ductless system).
Yes the thermal overload is covered by the resin and tape right on top of the winding. Sounds like you will need a new psc blower motor. They are not very expensive, thanks!
Light o rama
Yup, thanks Tom!
Better trash that motor pulling 30 amps 😂