Blower Motor Resistor?
Teching In
Joined: Mar 2019
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I'm having trouble to. Both of my fan come on at low speed, but want come on at high speed. I can command the fans to come on thru a program, but only the low speed, but the high speed does nothing. Where should I start?
Joined: Nov 2003
Posts: 11,331
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From: Jacksonville, FL (originally from Toronto Canada)
You seem to be talking about the engine fans while this thread is about the heating/air conditioning blower fan in the dash (there's only one).
There are three relays controlling the engine fans. They are located in junction block #1 under the hood on the left fender wheelhouse. Relay #1 controls the basic on/off function. The other two relays control the speed. In their rest position the fans run at low speed. When energized, they switch the fans to high speed. Given that, either both relays #2 and #3 are bad and need to be replaced or there is a problem with the PCM triggering the relays (possibly the dark blue wire from the relays to the PCM is broken or loose).
It would be best to start a new thread about engine fans if you need additional assistance.
There are three relays controlling the engine fans. They are located in junction block #1 under the hood on the left fender wheelhouse. Relay #1 controls the basic on/off function. The other two relays control the speed. In their rest position the fans run at low speed. When energized, they switch the fans to high speed. Given that, either both relays #2 and #3 are bad and need to be replaced or there is a problem with the PCM triggering the relays (possibly the dark blue wire from the relays to the PCM is broken or loose).
It would be best to start a new thread about engine fans if you need additional assistance.
Last edited by WhiteBird00; Sep 24, 2019 at 07:22 AM.
Teching In
Joined: Jul 2019
Posts: 37
Likes: 14
From: Canterbury, CT
Picking this thread up a bit late but hopefully, those in the know can help...
My 1999 Firehawk's blower motor only works on high. I suspect it is the blower motor resistor module as I have had this problem with older GM "A" body and "G" body cars. The resistor module was easy to locate and replace in the engine bay on these cars. On the 4th gen f-body, looks like some disassembly is required under the passenger side dash.
I decided to order the replacement part before pulling the carpet back and getting into the motor and electrics. I ordered this from RA:
ACDelco 15-5876 GM Original Equipment Heating and Air Conditioning Blower Motor Delay Module Kit
Obviously I should have taken a better look at the picture. Definitely NOT a blower motor resistor module, although Azn, RA and a few other sites state this is the direct fit Blower motor resistor for my 4th Gen bird TA.
The only site that lists what seems to be the correct part is Oriely AP. A Murray product, part number 20067. Special order and a bit pricey at $152!
https://www.oreillyauto.com/shop/b/c...ntiac/firebird
If that's the the right price, then I need to find an alternative.
As a last resort, I found the original AC Delco part number in the Parts listing PDF provided elsewhere in the forum (Thank you, contributor!).
That part number is 15-71979, A google search found a couple of vendors that list that part number (stockwiseauto for one) at half the Oriely's price, but they show Zero stock and no eta for new stock arrival. Wouldn't even let me add it to my cart!
https://www.stockwiseauto.com/acdelc...motor-resistor
I have searched this forum and googled my brains out and I can't find anything definitive for this replacement part. I'd like to order it and have it on hand before I jump in.
The next step is to pull out the old one and bring it to the local AP stores and see if they can find a replacement. Hopefully for less than the Oriely's $152 version!
Is thing another example of unobatinum? If so, what are my options, if any, beside getting the Murray part?
Any and all help appreciated.
Moderator, if I broke any rules posting the links, let me know and I'll modify my post...... my apologies.
My 1999 Firehawk's blower motor only works on high. I suspect it is the blower motor resistor module as I have had this problem with older GM "A" body and "G" body cars. The resistor module was easy to locate and replace in the engine bay on these cars. On the 4th gen f-body, looks like some disassembly is required under the passenger side dash.
I decided to order the replacement part before pulling the carpet back and getting into the motor and electrics. I ordered this from RA:
ACDelco 15-5876 GM Original Equipment Heating and Air Conditioning Blower Motor Delay Module Kit
Obviously I should have taken a better look at the picture. Definitely NOT a blower motor resistor module, although Azn, RA and a few other sites state this is the direct fit Blower motor resistor for my 4th Gen bird TA.
The only site that lists what seems to be the correct part is Oriely AP. A Murray product, part number 20067. Special order and a bit pricey at $152!
https://www.oreillyauto.com/shop/b/c...ntiac/firebird
If that's the the right price, then I need to find an alternative.
As a last resort, I found the original AC Delco part number in the Parts listing PDF provided elsewhere in the forum (Thank you, contributor!).
That part number is 15-71979, A google search found a couple of vendors that list that part number (stockwiseauto for one) at half the Oriely's price, but they show Zero stock and no eta for new stock arrival. Wouldn't even let me add it to my cart!
https://www.stockwiseauto.com/acdelc...motor-resistor
I have searched this forum and googled my brains out and I can't find anything definitive for this replacement part. I'd like to order it and have it on hand before I jump in.
The next step is to pull out the old one and bring it to the local AP stores and see if they can find a replacement. Hopefully for less than the Oriely's $152 version!
Is thing another example of unobatinum? If so, what are my options, if any, beside getting the Murray part?
Any and all help appreciated.
Moderator, if I broke any rules posting the links, let me know and I'll modify my post...... my apologies.
Last edited by gusser; Oct 24, 2019 at 03:44 PM. Reason: typo
Teching In
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Joined: Nov 2003
Posts: 11,331
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From: Jacksonville, FL (originally from Toronto Canada)
When you say your air stopped blowing do you mean that the fan doesn't blow air at all, regardless of using A/C or just vent? If so, have you checked the HVAC fuse? Don't rely on a visual inspection - a fuse (especially one that's 25 years old) can look fine but still be blown - always use a fuse tester, multimeter, or just replace with a known good fuse.
If the fan won't blow even on high speed then you can eliminate the blower resistor for now. The high speed setting doesn't pass through the blower resistor which is why it's an obvious diagnosis when high speed works but none of the other speeds do. Similarly, if all the other speeds work but high doesn't then it is almost certainly the blower relay.
You should always check for power and ground at the blower motor connector before replacing it. If you find both power and ground at that connector but the blower doesn't work then you can be certain that the motor is the problem.
If the fan won't blow even on high speed then you can eliminate the blower resistor for now. The high speed setting doesn't pass through the blower resistor which is why it's an obvious diagnosis when high speed works but none of the other speeds do. Similarly, if all the other speeds work but high doesn't then it is almost certainly the blower relay.
You should always check for power and ground at the blower motor connector before replacing it. If you find both power and ground at that connector but the blower doesn't work then you can be certain that the motor is the problem.
Registered User
Joined: Oct 2024
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I have no air coming out of any vents When you say your air stopped blowing do you mean that the fan doesn't blow air at all, regardless of using A/C or just vent? If so, have you checked the HVAC fuse? Don't rely on a visual inspection - a fuse (especially one that's 25 years old) can look fine but still be blown - always use a fuse tester, multimeter, or just replace with a known good fuse.
If the fan won't blow even on high speed then you can eliminate the blower resistor for now. The high speed setting doesn't pass through the blower resistor which is why it's an obvious diagnosis when high speed works but none of the other speeds do. Similarly, if all the other speeds work but high doesn't then it is almost certainly the blower relay.
You should always check for power and ground at the blower motor connector before replacing it. If you find both power and ground at that connector but the blower doesn't work then you can be certain that the motor is the problem.
If the fan won't blow even on high speed then you can eliminate the blower resistor for now. The high speed setting doesn't pass through the blower resistor which is why it's an obvious diagnosis when high speed works but none of the other speeds do. Similarly, if all the other speeds work but high doesn't then it is almost certainly the blower relay.
You should always check for power and ground at the blower motor connector before replacing it. If you find both power and ground at that connector but the blower doesn't work then you can be certain that the motor is the problem.
I don’t know if you will reply but I have no air coming out of my vents like the other guy, even on high. I have no power at the blower motor but all the fuzes are good, what’s the next steps? I thought it was the speed chooser (climate control actuator) and got like three from the junk yard but they all don’t work. Thanks
Joined: Nov 2003
Posts: 11,331
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
Let's start with what kind of vehicle do you have (year, make, model)?
Assuming a 4th generation f-body, have you tested the wires at the relay as described in post #10 above? What results did you get?
You mention that the fuses are good... did you test them or replace them with a known good fuse? Fuses - especially 25 year old ones - can be blown but still look fine, so never rely on a visual inspection. While you're at it, use a test light or multimeter to check that you have power to the fuse socket.
Let us know what your testing reveals and we'll try to provide additional direction.
Assuming a 4th generation f-body, have you tested the wires at the relay as described in post #10 above? What results did you get?
You mention that the fuses are good... did you test them or replace them with a known good fuse? Fuses - especially 25 year old ones - can be blown but still look fine, so never rely on a visual inspection. While you're at it, use a test light or multimeter to check that you have power to the fuse socket.
Let us know what your testing reveals and we'll try to provide additional direction.
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I've got a 2002 Trans Am, and the blower motor has stopped working on all speeds. I tested the blower motor itself by jumping the wires at the relay. When testing the blower motor switch, there is no power on the light-green wire, which I believe connects the mode selector switch. When I move the mode selector switch between the different options, I can hear vacuum and movement. I'm struggling to find where I should take my troubleshooting next.
Joined: Nov 2003
Posts: 11,331
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
I've got a 2002 Trans Am, and the blower motor has stopped working on all speeds. I tested the blower motor itself by jumping the wires at the relay. When testing the blower motor switch, there is no power on the light-green wire, which I believe connects the mode selector switch. When I move the mode selector switch between the different options, I can hear vacuum and movement. I'm struggling to find where I should take my troubleshooting next.
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Joined: Jan 2025
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Yes, fuse is good. I tested with my multimeter.
Also, tested everything from post 10. Red wire is always hot. No other wires show voltage. Purple obviously is good given that it turns the blower on when I jump it.
Also, tested everything from post 10. Red wire is always hot. No other wires show voltage. Purple obviously is good given that it turns the blower on when I jump it.
Last edited by CerealKiller19; Jan 6, 2025 at 05:07 PM.
Joined: Nov 2003
Posts: 11,331
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
Check for power on the brown wire at the mode selector switch. If you have power there but none on the light green wire (the output to the fan speed switch) when it is in any position other than OFF, then your mode selector switch is defective.
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I found the wiring harness was no longer attached to the back of the mode selector switch. Thanks.
Last edited by CerealKiller19; Jan 6, 2025 at 05:34 PM.
