How to understand 60's/70's/80's GM blower motor circuits
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- เผยแพร่เมื่อ 5 ก.ย. 2024
- These are all essentially the same with manual controls. Common problems such as no blower or only working on certain speeds can be easily repaired once you understand how the different devices operate.
Pretty amazing this video was posted 8 years ago and is still helping people out. Thanks, got my AC going again after this video.
9 year old video. Thanks a TON, exactly what I needed
Thanks... hearing you explain it helped me figure out how the high blow relay needs to be wired. I am replacing the old tin relay with a modern Bosch relay.
For anyone else who needs it:
85- ground
86- orange wire from resistor
87- battery voltage (20a fused, 12g minimum)
87a- blue wire from resistor
30- blower motor
9 years later, video is still helpful - you are right - this is the same sytem on my 85 Camaro and my 79 Caddy. My Caddy keeps blowing those relays.
Brother I have a 77 Corvette and couldnt find ANYTHING to explain this system as clearly as you did... from so called EXPERTS! Bless you... YOU have solved MY problem! Salute
Video is perfectly explained in terms I can understand, I replaced the resistor and blew it again putting my fan on high, so I replaced the motor and still don’t have high. Looks like I need to check the relay. So glad I found this video
Well you just kicked stupid out the window and brought back common sense.
Thanks for sharing your knowledge Fort Worth Texas appreciate you.
Blessings and more blessings to you and your family
Your a really good teacher, very well explained and understandable.
Thanks! It's not easy to explain this stuff sometimes.
This was an incredibly useful video, thank you mate!
I'm glad.
I have had college professors who could not explain their subject matter as well as you have done here. I'm going to call you Doctor fix it. Outstanding video explaining how this circuit for A/C works. im going to subscribe to you channel. Thanks a lot.
Thank you for this video. My wife's 1981 Pontiac Bonneville's AC just stopped blowing on high speed today, now we know where to start looking.
Thank you so much! I"m working on my 1980 Silverado that has a bunch of wires cut and missing. The manual does not show this detail - you saved me!
Even though this video is 8 years old, it helped me to finally understand that the blower motor was designed to be on low with the key on. It runs on LOW all the time.. OMG,!the hours I put into my 1979 GMC Caballero or El Camino, same basic layout. Now I can button her up and move on. Thank you very much. E The Swiss Army Knife
Right, gm refers to that as flow-through ventilation or astro ventilation
I'll get into the 68 today using your vid as a guide. Answered so many questions! Thank you!!
I just wanted to say thanks for taking the time to post these informational videos. I'm refurbishing my GMC G35 vandura at the moment and your clips are really helpful in understanding the basic principals of my vehicle. You have a very good way of describing things. So thanks!
Best explanation on the wiring, Thank you!
Finally a video for vintage factory a/c.
Thank you.
I’ve been searching for a helpful video on this subject for a long time!
Excellent explanation.. fixed my high speed blower after watching this ..thx
I have a 79 Camaro (Rally Sport) and the dash switch had burnt out and broken up internally so i finally found original switch ($50 for the models with A/C) but the pigtail plug from dash wiring is a little boogered where it got hot. Keep loosing connection on med. 1 and med. 2 at my switch. If i can ever find a NOS pigtail for it I will be aces then LoL. Ive considered cutting it off and just splicing on female slide disconnects but for the sake of simplicity and originality i haven’t done it yet. Thanks for being good at what you do, because of your videos my quadrajet that left me on the side of the road is now 100% rebuilt and running like a champ! All 4 barrels are doing exactly what their suppose to do. Once again, thank you thank you thank you! Ive also put many quadrajet haters in their place because of what you have taught me LoL.
Kris Denton what happened when the switch went bad? My blazer is blowing the fuse right after I turn those key, my best guess is the switch but I guess that why I’m here
Watching this was that breakthrough moment that let me diagnose my car.
Thanks for explaining this. I’m working on an 80 and the wiring has been hacked and butchered. The fan doesn’t try to work at all. This helps a ton.
One other thing about those relays is that they also sometimes stay stuck on the on position with the blower running on max with the key out of the ignition and the heater controls on off quick fix is to tap the top of the relay till the contacs inside disconnect. Happen to me a couple of times with new and old relays in that same GM setup. Could save you alot of headaches trying to figure out because it did for me.
Nice job explaining how the blower wiring works. Very helpful.
Just a little tip, as far as electrical theory, voltage doesn't actually flow-it's only the current that flows (ie, electrons moving through the wire). Voltage is basically the difference in "potential" between the positive (12V) and ground (0v), and the amount of current that flows depends on the difference in voltage between the two points (12 volt difference), and the amount of resistance in the circuit (resistors, wires, and anything else in the circuit that resists the flow of the electrons). So basically, 12 volts doesn't "come in" to the motor, as voltage doesn't travel-it's only the current that flows (hence the rating of fuses in amps-which is a measure of the amount of current that the circuit can handle, before the wire would melt or catch fire). Hope that helps! Thanks for your videos, they're very informative, and I appreciate the friendly style as well
Thanks for the tip!
WhoSaidTyler You're welcome! And thanks again for the videos!!
You have a teaching gift, glad you are using it productively
thank you for blessing the world with this useful video.
Fantastic video. I needed this to fix my 87 v30. Thank you
You're welcome!
Awesome! I have been trying to get my heater to work for a while now and I’m so glad you had a great vid to explain it!
Wow he explained the whole circuit for heater
made it sound easy great video.
Well done looks much better and man ide love to be able to leave tools outside!! Leaving a car out front is questionable were I live 😅
Great video, helped a lot. Working on my 77 c-20 and the whole ac system is getting a rebuild from scratch so this is helpful.
That 77 c20 is worth a lot now. Any money you put into it now is well worth it. Auto metal direct can help out with rusted out body panels., hoods and doors.
Might be an old video but it’s greatly appreciated
Thank you
We sure are lucky you can translate these technical things into southern.
Now I understand. Thanks my 73 lemans thanks you too.
Awesome!
@@TylersNeighborhoodGarage joking aside you really did a great job explaining that..much appreciated, now I think I have a fighting chance, my fuse keeps burning out like I got a short..fan?
on a side note I took the control panel out and cleaned and relubed all moving parts..it operates like brand knew..seems all that old grease drys out.. cheers
Great job explaining. My 79 TA is blowing the fuse under the dash when turned to high. I will be ordering a new relay I think.
Working on a 1981 Chevy C10 and this helped a lot! Thanks
Thanks for going through that so thoroughly!
Thank you for making this. It's very helpful as I look at what missing in my 78.
Very helpful! Thank you for sharing.
My high speed fan stopped working I replaced the relay still did not work removed relay checked the red wire for voltage had 12 volts run a jumper wire from the red wire to the fan motor it would not run checked for voltage again still had 12 volts started tracing red wire come to a connector with three other wires pulled the connector apart red wire connection was burnt it had enough connection to read the 12 volts but when you put a load on it it lost connection spliced the wires together now she blows on high speed thanks for the video Tyler
Tyler, thanks so much for your helpful videos. You are a good dude.
The blower on '76 Buick Super required the left fender to be removed in order to replace the blower motor. The blow motor always ran, which shortened the life of the blower motor.
Thanks for the explanation. Mine turned out to be the switch itself, which is really a good thing because I didn't have to monkey around with the resistors.
Super helpful video. Thanks!
Thankyou! This will help me out on my 81 k20 project. It's a wiring disaster
Thanks for this, defintely gave me an understanding of what to look for
Thanks you taught me a lot.
Thank you so much. This is exactly what I needed to know.
good explanation. I was able to find the wrong size fuze in the panel and then the wire wasn't connected to to the blower motor.
Best video I’ve ever seen 🎉🎉
Great video! Helped me improve my understanding of my C3 corvette system too. 👍
Thanks for posting this trying to fix Wifes 79 el camino blower wont work on high. Now I think I can figure it out!
Sure, just remember that the switch doesn't pass the current on high. It merely turns on the high speed relay.
@@TylersNeighborhoodGarage Just like you said my problem is the high speed relay. Thanks for your help.Do you know anything about gm charging systems of this vintage.my gen light is on.Alt is charging @14.5 volts?
Thanks, this should help me figure out my 1978 G20 blower resistor previous owner hack.
You saved my ass with this data. Thanks!
Thanks for the great video explaining how the system works. I just purchased a 1974 chevy stepside a few months ago and slowly doing some repairs. When I turned on the heater and defroster, the system appears to work but there is a loud whine. Since the electricle seem to be working, I am wondering if best to start by checking the blower motor? Do you have any videos of actually pulling that out and cleaning? Or replacing? Thank you
Subscribed and liked. Thanks for sharing this info in a simple way.
1980 GMC keeps popping the fuse switching on high new relay and resistor any suggestions thank you
Great video! Thanks!! How does the blower get power to always blow on low when the schematic shows the temp and a/c selector switches have a open on the input power from the fuse box when both are in the off (all the way left) position?
I think I could tackle the job now if I ever get an opportunity to work on one. Hope to get a short bed Chevy one day.
Excellent video…valuable information
Glad you liked it
You saved me hundreds....thx
My brother's truck keeps blowing the fuse when the blower is set to high. Trying to figure out what it can be. We have replaced almost the whole system. We are leaning that the wire itself must be the problem. It has a new resistor, new relay, new blower motor and we tried a new switch on the climate control. Yep we just started throwing parts at it because the previous owner had it all tore apart.
Wish I would have found this video a while back. I burnt up factory switch cause I bypassed resister and relay. Then I tried running just a 15 Amp on/off switch from auto zone and melted it too. I didn't realize the blower motor pulled so many amps. I know now!
Thanks. Now I understand why high speed doesn't run. The big red power wasnt going to the relay. Thanks
I have 12v at my relay the relay is testing good the speed control switch inside has no voltage my fan works the resistors are good the blue wire from the resistor to the relay is good still not working I’m gonna try replacing the relay and see if that fixes it but I’m unsure if that doesn’t do it
so on the fender mounted bus bar does that have constant 12 v to relay ?
Great video. On my 78 Cadillac coupe, the AC blows only in low even if the setting is on High. But I noticed under the hood, the brown wire that's connected to the blower is disconnected and has a red jumper wire connected to the connector terminal that is on I guess it's the resistor, there is only 3 wires leading into the connector. I've never disconnected it or made an attempt to see what it does if I remove the red jumper wire and reconnect the brown wire in fear that it would fry it and then I'll have no more AC. Now I've used the heat and works on high setting but blows low? 🤷♂️ thoughts?
A very good explaination of how this circuit all works. My problem is I have a 69 chevelle same wiring diagrahm with air cond. When I go down the road with the air on after about a half hour or so give or take 30 minutes it blows the fuse. Air is working fine which is drawing about 5 amps when running when I check the purple wire with the fan on high speed and the air on it will spike to about 18 amps. Could it be the resister or relay thats causing the blown fuse.
unplug the blower does fuse still blow?
Thank you posting this, very helpful
Most blower fans have straight 12 volts to the motor and they ground back through the resistor thanks to the switch to vary the speed
i have a 76 k10, i can hear blower motor running when truck is not running,. after starting and trying to turn fan speed up it does not go faster, no speed change. I dont know how to test ,where to start? Also my accumilater doesnt have that switch? on left side of it ,is that needed? thanks
super helpful video dude
I have a 1970 El Camino; the fan blower motor switch keeps getting hot and burning out upon occasion; I've replace the fan switch 3 times; I don't know why it gets hot; do you have a solution? Also, I recently purchased a new fan switch; and blower motor. I can change out the switch easily enough; but honestly, I don't know where the blower motor is located; I think it may be under the dash somewhere because when it was on, I could heard it running, but the design underneath the dash below the glove box is strange to me; nothing is obvious like it would be seeing it on the fire wall on a C10 truck.. If you have a video of how to replace the blower motor on a 70 El Camino, I would sure appreciate that help. Thank you.
That problem exists on a 1983 Monte Carlo when you turn the gauges on the dash to heat the blower motor positive and the negative are registering hot on a meter can you help me with this problem
Hey brother I am having issues with my fuses popping when I turn my switch from the off position. I’ve put on a new relay and resistor as well as a new switch control. I’ve gotten it to run intermittently for about twenty minutes and then that fuse will go. I’ve disconnected the resistor all together and it’s working for now but the darn thing is new so I’m hoping that it’s bad out the box. How would I know if it is my issue causing fuses to blow?
My blower only work on Hi. Low and Medium doesn't work. So I replaced that resister. But it didn't fix the problem.Then I replaced the A/C fan blower switch, that wasn't there problem either. Any other ides?
Great explanation. When I turn the heat on in my 65 LeSabre, the blower kicks on only when I put into gear and start driving. Sometimes it'll come right on, sometimes cool sometimes worm. Today I noticed the orange wire coming off the resistor circuit attached to airbox getting so hot it lights up, melting the insulation. This only happens when the heat is on. Any idea where I should start? Thanks
Thanks for your video. My blower hasn't worked in 10 years. Finally decided to get it working. This helped. But know I'm having a vacuum issue my blend doors dont work. all my hoses ( check valves if needed) from the reservoir to the manifold are gone. Do you have a video on this.
Can you show were the vacuum line goes to
Where is the fuse located in the fusebox for the blower motor?
My 78 is the same way, my switches aren't working but it's idling at one speed, I put new ground a new blower and the switch worked before but it's a new blower but won't turn on high, how did you fix yours?
I have a 66 lemans that the blower motor doesn't blow air at all, No matter what position the switch is. The switch, or a relay? It doesn't appear to have blown fuse.
Which fuse it? Is it one of those metal case type fuses? My blower used to work on low, but now not at all even after replacing switch. Thinking it may be resistor.
Thanks for this great video. I was replacing the speakers in my 1975 Cadillac Deville so I had to take the dashboard apart. After putting it back together, I realized the blower motor isn't working anymore when I put the key in. It only works on defrost now. What would cause such a situation? I'm guessing I messed up something when putting the dash back together, but I can't seem to figure it out.
I have a 1984 with a none working blower .. Blower works with a direct power to it .But not working at all hook up with factory set up Fuse still good what would the next step .. with out replace everything . There is 12 volt at block on the fire wall ..
Ok, the colors appear to be a little different on my 72 Riviera. Here's what I found.
Blower motor resistor:
Term 1: orange wire to blower relay
Term 1 to 2: 0.4 Ohms (medium 2 - black w/ blue stripe)
Term 1 to 3: 1.0 Ohms (medium 1 - tan wire)
Term 1 to 4: 2.4 Ohms (low - brown wire)
Blower motor relay (2 connectors):
3 post connector: (Orange wire from resistor, medium gauge black wire with orange stripe to fan, and heavy gauge blackish(?) wire with constant 12 volts any time the battery is connected)
2 post connector: (Small gauge black wire and small gauge black with orange stripe)
I could not figure out what the black wire goes to, no continuity to ground or positive on battery.
Switch:
Switch in low = 12v on brown wire
Switch in med 1 = 12v on tan wire
Switch in med 2 = 12v on black w/ blue stripe wire
Switch in high = 12v on small gauge black w/ orange stripe wire that goes to relay
I bypassed the relay altogether to test the low, med1, and med2 speeds but still did not get a low speed fan, only med1 and med2.
With the battery disconnected to avoid arcing, I jumpered the heavy gauge constant 12v wire to the blower wire (medium gauge black w/ orange stripe). Upon reconnecting the battery I got high speed blower.
My vehical is doing the same exact thing I've changed resistor and relays but to no avail
I have 1988 S-10 fan only blows on high. I change resistor did not help. Where do I go now?
Best explanation 👌. Thank you
You are welcome
From the 12v distribution block,there is a inline fuse on the orange wire that leads to the relay. What size amp should thay fuse be?
I was wondering why my blower was running with the key on and the switch turned off now i know! Thanks!
Yes, "Flow-thru" ventilation
If it has a bypass for all non-max blower power inputs until the coil is energized, I can assume it's an SPDT style relay?
mine works on all speed but on hi. put it on hi and the motor shuts off . it’s a 75 gmc big block suburban.
Having an issue with my 84, if I take a wire and connect the battery to the fan it runs just fine but soon as I connect the wiring harness with the fan to the relay it doesn’t come on at any speed. I took a multimeter and I’m getting 13 volts to the red wire on the harness. The fuse is fine as well. I’ve done tried 2 brand new relays and still can’t get anything going. I cleaned the grounds as well.
On new cars it’s easy if the fan works on the highest setting but not on any of the lower settings it’s the resister cause on the high setting it’s direct 12 volts too the fan. If none of the settings work not even the highest setting it’s the fan it’s self that’s broken
Thank you for such an informative video on the heater blower motor circuit! I have a question... I have a 78 chevy c10 with AC. the blower runs on low, m1, m2, but not on High. I have replaced the blower motor, relay, and resistor. I am also getting power to the relay from the switch. Any help would be appreciated Thanks again
It will be standard test procedure from here on. You simply trace power from it's source to it's destination and determine where it "stops". At this point I would focus on the wiring to and from the relay. The relay has load in, load out, a trigger from the switch and a ground. Check carefully.
@@TylersNeighborhoodGarage Thank you for all your help and reply!!! Will try to make some of these tests tomorrow. Thanks for taking time to assist with these issues! I really appreciate it.
Why is the ac pump on the driver side? Mine have always been on the passenger side. Am I tripping?
Thank you. I needed this video. Mine doesn't work on high speed everything else works. I think the switch inside truck is bad
Glad it helped
I put in an ac delete panel on my 1971 Monte Carlo. I cut a hole in new panel and took resistor off ac unit and installed . The dark blue wire is not connected and the tab where it goes is broken off. The fan doesn’t work at all. I’ve been working on this for days . Any thoughts? I can hear a springy noise coming from relay ( the first metal box) when I flip selector switch to high but yeah it doesn’t work at all now.
I got power to the resistor and to the relay but nothing in the two wires going to the blower motor on a 79 trans am, so blower isnt working on any speed
My issue is I can't find the fuse. I want to start there cuz I don't read voltage on blower plug.
I checked the circuit and jumped it and the fan ran on high sped so i replaced the switch and it ran for a few seconds and it stopped so what happened?