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Recently, I spent a lot of time troubleshooting, researching, and throwing various unnecessary parts to resolve issues with my 7th Gen HVAC Blower Motor. I wasted a little money and time, but in the end probably still came out ahead vs. a shop fix (luckily).

Absense of a defogger or heat in the winter could be a safety hazard, so I can definitely sympathize with some of you in cold weather climates having this problem. Thanks, GM.

This is for models with the standard manual switch controls in the dash (fan speed, hot/cold for driver/passenger, air flow setting, A/C button, vent control), a blower resistor module (not a standard old-school resistor screwed into the blower, but the actual 5-plug harnessed computer module/resistor chip looking thing, ACDELCO part 1581727, under the passenger side dash), and of course the blower itself.

I finally found the problem after a while, but not after chasing ghosts. I decided to summarize what I've learned in the hopes that maybe it will help someone else avoid the same pitfalls.

Admins, feel free to delete if it's not helpful.

There are several threads and posts about this issue all over the web for 7th gen Impalas, and other GM models around the same year, so really this is just an aggregation of my findings. It's not an exhaustive list, nor is it intended to be, but maybe it can help someone at least get started on finding the problem. Many, many GM models have this setup.

One distinction I've seen among many is that the 2004-2005 Impalas and Montes have the 10-setting fan speed switch, and the earlier years have the 5-setting fan speed switch.

First things first, I recommend purchasing an inexpensive multimeter. If you aren't sure how to use one, turn it on, set it on voltage reading, and calibrate red/black on the battery terminals so that you're getting a ~ 12 volt reading. This way, you know you have it set up correctly when testing an actual terminal. There are plenty of how-to's on the web, and they can really help diagnose electrical issues and save you money.

Rarely, if ever, have I seen a switch replacement solve any of these problems based on my research, but if your vents aren't responding to the settings, and the rear defog isn't working, or your lights are all dead in the fan switch controls, then you may have an issue with the switch itself. Again, this is rare, and if you do think you have a faulty switch, I would test with a scrapyard piece before wasting money on a new one.


Now, for the symptoms and possible resolutions:
=================================================

Symptom: Blower motor only working on certain settings. The 2004-2005 has the 10-setting switch, and prior
years have the 5-setting switch. Blower motor also may run with the key off.

Possible resolution: The blower motor control module seems to be the culprit for this problem based on what I've seen in several other threads and sites. You will definitely want to confirm that you are getting steady voltage to the module before wasting your time replacing it. Based on the fact that you're still getting power to the module and the fan, there is likely an issue internally with the blower control module/resistor. You can utilize the multimeter to test steady voltage to the blower control module by locating the blower control module harness under the passenger side kick panel (it comes down by pressing in two black tabs under the glovebox). Disconnect the 5-plug harness from the module, locate the red and black wires, turn fan to high, and test voltage with multimeter to confirm. If voltage is steady at ~ 12 volts, and it does not fluctuate, then the module is in all likelihood in need of replacement. To replace, you will see a link below for a how-to, and there are other how-to's on the web for this. If it's the original factory module, you will need a small chisel to get the old one out, and some screws to secure the new one in place, but it's actually not too bad. AC Delco part # 1581727, try Amazon.com or Rockauto.com for best pricing. I have found that a lot of times this is actually not the problem if the blower isn't working on any speeds, but many believe it is, so I recommend testing thoroughly before replacing. Variation in behavior based on speed setting is the only thing that seems consistent in terms of when this thing really fails on you and needs replaced, but perhaps others have a different opinion.

Symptom: Blower motor not working at all on any speed setting, and it never works at all. It never works while driving, it never works when turning the key to start->on. It never works on any speed setting. It's always dead. You have power to the switch, vent controls are working, rear de-ice is working, but blower is completely dead.

Possible resolution: Check the HVAC blower fuse in the fuse panel first, and the relay under the hood (passenger side relay box). These should be the first places you check. Replace if fuse/relay are burnt or broken. Turn on and test the fan. If the fuse/relay is good, your blower motor itself might be bad. The way to find out is by dropping the passenger side kick panel down under the glove box. Disconnect the two wire black/purple harness from the blower itself. Black is ground, purple is hot. Turn the fan switch to an on setting, and verify you are getting voltage at the blower motor. On high, the voltage should be close to ~ 12 Volts. If voltage is steady, then this confirms that you are getting power to the blower motor, but the blower motor is not turning. If you are not getting voltage, test the main hot wire to the blower control module. Disconnect the main 5-wire harness to the module, set fan switch to high, test red/black for ~ 12 V. If you are getting voltage, then this could be the blower motor itself. AC Delco part # 1581726, try Amazon.com or Rockauto.com for best pricing.

Symptom: Blower motor only works when you're messing with the key in the ignition, turning on to start, or halfway between, or some variation in where your key happens to be at a specific point in time. Intermittently works when activating ignition via the key. Blower motor also may run with the key off.

Possible resolution: Ignition switch or ignition switch relay is faulty. The ignition switch and switch relay do control continuity to accessories. You may notice other accessory or lights working intermittently based on where the key happens to be in the ignition switch. This seems to be a more common problem on 2003's and older. Replacing the ignition switch is actually a very easy thing to do, I see some of the members saying the dealer is quoting $300+ to replace it, if you have some patience and basic hand tools, you can easily do it yourself. The AC Delco part # for the switch is AC Delco #D1432D, and the relay is AC Delco # D1786C. Also, there is a Tech Service Bulletin for Pontiacs and Buicks with the same setup - in my case, the TSB did not resolve my issue, but it's a fairly cheap/easy thing to try, and solder in my mind is optional. GM Service Bulletin No.: 05-01-39-001A - The capacitor is AC Delco part #25073556, reasonably priced on Amazon. I wonder if installing this capacitor, if anything, may extend the life of your blower control module, since it will help regulate the power and may keep heat on the wire to a minimum. Ironically, this is the hardest issue to find, but probably the cheapest one to fix! I was not able to find a part number for this harness, but based on what I have seen, it's not set up to handle the amperage from the HVAC system anyway, so a splice may actually be better than a full harness replacement, not sure.

Symptom: Blower motor works intermittently without any predictability. It will work for a while, and then stop working when hitting bumps, braking, or utilizing more accessories (radio, headlights, defogger). Fuses and relays look fine. Banging the dashboard under the radio or under the glovebox seems to trip it back on sometimes, or will kill it. Fuses and relays are fine. Sometimes, you can hear the blower trying to kick on, but it's barely turning - voltage is weak or non-existant at the hot wire in the 5-wire blower control module harness for a while, and then will suddenly return.

Possible resolution: Potential issue with HVAC wiring harness under the ashtray. This harness connects main power and triages the fan speed/vent switch to the blower control module and blower. Sometimes, you will turn the fan to on and hear a click like something is trying to turn on, and you will feel weak air trying to blow through the vents, but not nearly enough to heat/cool the interior. You'll be driving, and suddenly the fan stops, and turns back on again a while later, sometimes minutes or even days later, without any rhyme or reason. When the fan is in dead mode, test the main hot wire going into the blower control module harness. If you are not getting voltage, remove the ashtray (4 screws). This can be tricky since the power could return based on vibration or arcing going on in the harness. Above where the ashtray mounts, you will see a harness fastened to a metal plate in the dashboard. Inspect this harness. The red wire in the harness is the main hot wire supplying power to the HVAC blower system. If the red wire appears burnt, has copper exposure, or the harness ports itself look burnt or discolored, then this may be your issue. I would say a broken or loose wire anywhere in the dash could be causing this issue, in my case, this was the one. If the red wire seems ok, then it's possible you have an issue somewhere else in the dashboard wiring, and/or you may need a secondary ground. If the red wire in the harness on either side is bad, disconnect the battery, cut the red wire going into the harness on both sides, and splice both ends together using a new piece 10 gauge wire and 10-12 AWG Butt splices. Reconnect everything, and test the blower, and make sure the blower is running, and the wire is staying nice and cool. If it works, this was your issue, if it doesn't, then you have an issue somewhere else in the dashboard wiring itself. If you are getting good voltage at the harness under the ashtray, but it's dying at the blower control module itself (test both ends), it may be the 5-wire harness for the blower control module itself. This is fairly inexpensive part, AC Delco part #PT795 (around $40 at the dealer, but you may find it cheaper elsewhere).


Various info and links
=======================

AC Delco parts summary (2004 Impala but other years with same setup probably the same #'s)

Blower Control Module/Resistor: AC Delco part # 1581727
Ignition Switch: AC Delco #D1432D
Ignition Switch Relay: AC Delco # D1786C
Capacitor for TSB 05-01-39-001: AC Delco part # 25073556
5-wire harness for Blower Control Module/Resistor: AC Delco part #PT795

Links to recent threads about this problem
http://www.impalaforums.com/chevy-impala-7th-gen-discussion/336168-blower-motor-cutting-out-help.html.
http://www.impalaforums.com/chevy-impala-7th-gen-discussion/335678-2004-blower-motor-issues.html

Link to blower module/resistor replacement tutorial
http://www.impalaforums.com/diy-do-it-yourself-how-to/299606-blower-motor-resistor-replacement-tutorial.html

Link to King's ignition switch replacement tutorial
http://www.impalaforums.com/diy-how-tos-and-write-ups/335250-7th-gen-ignition-switch-replacement-access.html

Dashboard removal how-to if replacing ignition switch or fan speed switch (not required to remove ashtray)

Tools required: 1 Phillips screwdriver

1. Open front doors and leave them open. Remove the exposed left and right fuse panel covers by pulling straight out with a finger in the hole. Remove single Phillips screw from each end of the dashboard plastic where it wraps around.

2. Remove two screws from the dashboard above the instrument cluster.

3. Depressing two clips, lower the plastic cover above the foot pedals and let it hang carefully on the footlight wires exposing two screws holding a panel below the steering column.

4. Remove the two screws from this panel, lower the front slightly and pull it towards the steering wheel. It should pop off exposing a single screw on the bottom of the dashboard plastic to the left of the steering column.

5. Remove this single screw and the whole dashboard can now be pulled off from around the instrument cluster, radio and steering column for its full length. The heater vents come with it. Pry gently but firmly with fingers across the top and bottom, back-and-forth across the full width until all the dashboard clips snap out. The steering wheel should be lowered fully and the gear lever put in first gear to get it out of the way. This will require having the key in and in the ON position. The dashboard will pull over the key. There is a plastic insert with the off/on/acc. key positions which snaps over the key lock and it may come off with the dashboard. Once the dashboard is reinstalled simply snap it back in. Once all the clips have released pull the top of the dashboard toward you carefully so the four-way flasher switch on the upper right of the cluster is clear of the top of the dash. Squeeze the clip and remove the plug from the back of the switch. This done, the whole dashboard can be removed carefully from the car. It is long and flimsy.

6. There are four screws holding the exposed instrument cluster in place. Remove them and pull the cluster gently towards the steering wheel exposing the single wiring harness plugged into the top right of the cluster. Squeeze the single tab on the plug fully and pull it out of the cluster. Remove the cluster fully from the dash.
 

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2004 Impala
Thanks for the trouble shooting steps and tips. I have been having an intermittent blower motr issue for the past 4-5 months. I would try something and it would start working and a couple days to weeks it would stop again Finally ran a jumper from the battery to positive pin on the resistor connector and everything worked. Tracing positive wire back I found the following connector behind the ashtray. I bought this car new so I know this is hasn't been touched since the factory install.
 

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2004 Impala

Thanks for the diagnosis and trouble shooting tips. After 4-5 months of hit and miss I finally ran a jumper wire from my battery to positive connection on the resistor and everything worked, i traced the wire back to a connector behind the ashtray and found the positive connection burnt. I have owned the car since new and I know that this connection hasn't been messed with since factory install





 

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Yes the wife's HVAC back online in her '05 Impala ! Yay !

:eek:k3: Thanks for taking the time to have researched this and posted it, saved me hours of chasing the problem and diagnosed the culprit almost immediately, upon inspection...had already gone through the fuses and was convinced it was the switch until reading this article
It was the blower motor just about to go out completely.
Come on go off worked when it wanted to...thing almost got my fingers while had it in the floor of the car plugged in and cycling the switch:giggle:..Picked up a VDO with limited lifetime warranty for just under $90.00 bucks at the local parts house..
Was an easy R & R hangin' onto the old one just in case, it still works sort of and it might make a good target one day... I like shooting up stuff that is broken...

Recently, I spent a lot of time troubleshooting, researching, and throwing various unnecessary parts to resolve issues with my 7th Gen HVAC Blower Motor. I wasted a little money and time, but in the end probably still came out ahead vs. a shop fix (luckily).

Absense of a defogger or heat in the winter could be a safety hazard, so I can definitely sympathize with some of you in cold weather climates having this problem. Thanks, GM.

This is for models with the standard manual switch controls in the dash (fan speed, hot/cold for driver/passenger, air flow setting, A/C button, vent control), a blower resistor module (not a standard old-school resistor screwed into the blower, but the actual 5-plug harnessed computer module/resistor chip looking thing, ACDELCO part 1581727, under the passenger side dash), and of course the blower itself.

I finally found the problem after a while, but not after chasing ghosts. I decided to summarize what I've learned in the hopes that maybe it will help someone else avoid the same pitfalls.

Admins, feel free to delete if it's not helpful.

There are several threads and posts about this issue all over the web for 7th gen Impalas, and other GM models around the same year, so really this is just an aggregation of my findings. It's not an exhaustive list, nor is it intended to be, but maybe it can help someone at least get started on finding the problem. Many, many GM models have this setup.

One distinction I've seen among many is that the 2004-2005 Impalas and Montes have the 10-setting fan speed switch, and the earlier years have the 5-setting fan speed switch.

First things first, I recommend purchasing an inexpensive multimeter. If you aren't sure how to use one, turn it on, set it on voltage reading, and calibrate red/black on the battery terminals so that you're getting a ~ 12 volt reading. This way, you know you have it set up correctly when testing an actual terminal. There are plenty of how-to's on the web, and they can really help diagnose electrical issues and save you money.

Rarely, if ever, have I seen a switch replacement solve any of these problems based on my research, but if your vents aren't responding to the settings, and the rear defog isn't working, or your lights are all dead in the fan switch controls, then you may have an issue with the switch itself. Again, this is rare, and if you do think you have a faulty switch, I would test with a scrapyard piece before wasting money on a new one.


Now, for the symptoms and possible resolutions:
=================================================

Symptom: Blower motor only working on certain settings. The 2004-2005 has the 10-setting switch, and prior
years have the 5-setting switch. Blower motor also may run with the key off.

Possible resolution: The blower motor control module seems to be the culprit for this problem based on what I've seen in several other threads and sites. You will definitely want to confirm that you are getting steady voltage to the module before wasting your time replacing it. Based on the fact that you're still getting power to the module and the fan, there is likely an issue internally with the blower control module/resistor. You can utilize the multimeter to test steady voltage to the blower control module by locating the blower control module harness under the passenger side kick panel (it comes down by pressing in two black tabs under the glovebox). Disconnect the 5-plug harness from the module, locate the red and black wires, turn fan to high, and test voltage with multimeter to confirm. If voltage is steady at ~ 12 volts, and it does not fluctuate, then the module is in all likelihood in need of replacement. To replace, you will see a link below for a how-to, and there are other how-to's on the web for this. If it's the original factory module, you will need a small chisel to get the old one out, and some screws to secure the new one in place, but it's actually not too bad. AC Delco part # 1581727, try Amazon.com or Rockauto.com for best pricing. I have found that a lot of times this is actually not the problem if the blower isn't working on any speeds, but many believe it is, so I recommend testing thoroughly before replacing. Variation in behavior based on speed setting is the only thing that seems consistent in terms of when this thing really fails on you and needs replaced, but perhaps others have a different opinion.

Symptom: Blower motor not working at all on any speed setting, and it never works at all. It never works while driving, it never works when turning the key to start->on. It never works on any speed setting. It's always dead. You have power to the switch, vent controls are working, rear de-ice is working, but blower is completely dead.

Possible resolution: Check the HVAC blower fuse in the fuse panel first, and the relay under the hood (passenger side relay box). These should be the first places you check. Replace if fuse/relay are burnt or broken. Turn on and test the fan. If the fuse/relay is good, your blower motor itself might be bad. The way to find out is by dropping the passenger side kick panel down under the glove box. Disconnect the two wire black/purple harness from the blower itself. Black is ground, purple is hot. Turn the fan switch to an on setting, and verify you are getting voltage at the blower motor. On high, the voltage should be close to ~ 12 Volts. If voltage is steady, then this confirms that you are getting power to the blower motor, but the blower motor is not turning. If you are not getting voltage, test the main hot wire to the blower control module. Disconnect the main 5-wire harness to the module, set fan switch to high, test red/black for ~ 12 V. If you are getting voltage, then this could be the blower motor itself. AC Delco part # 1581726, try Amazon.com or Rockauto.com for best pricing.

Symptom: Blower motor only works when you're messing with the key in the ignition, turning on to start, or halfway between, or some variation in where your key happens to be at a specific point in time. Intermittently works when activating ignition via the key. Blower motor also may run with the key off.

Possible resolution: Ignition switch or ignition switch relay is faulty. The ignition switch and switch relay do control continuity to accessories. You may notice other accessory or lights working intermittently based on where the key happens to be in the ignition switch. This seems to be a more common problem on 2003's and older. Replacing the ignition switch is actually a very easy thing to do, I see some of the members saying the dealer is quoting $300+ to replace it, if you have some patience and basic hand tools, you can easily do it yourself. The AC Delco part # for the switch is AC Delco #D1432D, and the relay is AC Delco # D1786C. Also, there is a Tech Service Bulletin for Pontiacs and Buicks with the same setup - in my case, the TSB did not resolve my issue, but it's a fairly cheap/easy thing to try, and solder in my mind is optional. GM Service Bulletin No.: 05-01-39-001A - The capacitor is AC Delco part #25073556, reasonably priced on Amazon. I wonder if installing this capacitor, if anything, may extend the life of your blower control module, since it will help regulate the power and may keep heat on the wire to a minimum. Ironically, this is the hardest issue to find, but probably the cheapest one to fix! I was not able to find a part number for this harness, but based on what I have seen, it's not set up to handle the amperage from the HVAC system anyway, so a splice may actually be better than a full harness replacement, not sure.

Symptom: Blower motor works intermittently without any predictability. It will work for a while, and then stop working when hitting bumps, braking, or utilizing more accessories (radio, headlights, defogger). Fuses and relays look fine. Banging the dashboard under the radio or under the glovebox seems to trip it back on sometimes, or will kill it. Fuses and relays are fine. Sometimes, you can hear the blower trying to kick on, but it's barely turning - voltage is weak or non-existant at the hot wire in the 5-wire blower control module harness for a while, and then will suddenly return.

Possible resolution: Potential issue with HVAC wiring harness under the ashtray. This harness connects main power and triages the fan speed/vent switch to the blower control module and blower. Sometimes, you will turn the fan to on and hear a click like something is trying to turn on, and you will feel weak air trying to blow through the vents, but not nearly enough to heat/cool the interior. You'll be driving, and suddenly the fan stops, and turns back on again a while later, sometimes minutes or even days later, without any rhyme or reason. When the fan is in dead mode, test the main hot wire going into the blower control module harness. If you are not getting voltage, remove the ashtray (4 screws). This can be tricky since the power could return based on vibration or arcing going on in the harness. Above where the ashtray mounts, you will see a harness fastened to a metal plate in the dashboard. Inspect this harness. The red wire in the harness is the main hot wire supplying power to the HVAC blower system. If the red wire appears burnt, has copper exposure, or the harness ports itself look burnt or discolored, then this may be your issue. I would say a broken or loose wire anywhere in the dash could be causing this issue, in my case, this was the one. If the red wire seems ok, then it's possible you have an issue somewhere else in the dashboard wiring, and/or you may need a secondary ground. If the red wire in the harness on either side is bad, disconnect the battery, cut the red wire going into the harness on both sides, and splice both ends together using a new piece 10 gauge wire and 10-12 AWG Butt splices. Reconnect everything, and test the blower, and make sure the blower is running, and the wire is staying nice and cool. If it works, this was your issue, if it doesn't, then you have an issue somewhere else in the dashboard wiring itself. If you are getting good voltage at the harness under the ashtray, but it's dying at the blower control module itself (test both ends), it may be the 5-wire harness for the blower control module itself. This is fairly inexpensive part, AC Delco part #PT795 (around $40 at the dealer, but you may find it cheaper elsewhere).


Various info and links
=======================

AC Delco parts summary (2004 Impala but other years with same setup probably the same #'s)

Blower Control Module/Resistor: AC Delco part # 1581727
Ignition Switch: AC Delco #D1432D
Ignition Switch Relay: AC Delco # D1786C
Capacitor for TSB 05-01-39-001: AC Delco part # 25073556
5-wire harness for Blower Control Module/Resistor: AC Delco part #PT795

Links to recent threads about this problem
http://www.impalaforums.com/chevy-impala-7th-gen-discussion/336168-blower-motor-cutting-out-help.html.
http://www.impalaforums.com/chevy-impala-7th-gen-discussion/335678-2004-blower-motor-issues.html

Link to blower module/resistor replacement tutorial
http://www.impalaforums.com/diy-do-it-yourself-how-to/299606-blower-motor-resistor-replacement-tutorial.html

Link to King's ignition switch replacement tutorial
http://www.impalaforums.com/diy-how-tos-and-write-ups/335250-7th-gen-ignition-switch-replacement-access.html

Dashboard removal how-to if replacing ignition switch or fan speed switch (not required to remove ashtray)

Tools required: 1 Phillips screwdriver

1. Open front doors and leave them open. Remove the exposed left and right fuse panel covers by pulling straight out with a finger in the hole. Remove single Phillips screw from each end of the dashboard plastic where it wraps around.

2. Remove two screws from the dashboard above the instrument cluster.

3. Depressing two clips, lower the plastic cover above the foot pedals and let it hang carefully on the footlight wires exposing two screws holding a panel below the steering column.

4. Remove the two screws from this panel, lower the front slightly and pull it towards the steering wheel. It should pop off exposing a single screw on the bottom of the dashboard plastic to the left of the steering column.

5. Remove this single screw and the whole dashboard can now be pulled off from around the instrument cluster, radio and steering column for its full length. The heater vents come with it. Pry gently but firmly with fingers across the top and bottom, back-and-forth across the full width until all the dashboard clips snap out. The steering wheel should be lowered fully and the gear lever put in first gear to get it out of the way. This will require having the key in and in the ON position. The dashboard will pull over the key. There is a plastic insert with the off/on/acc. key positions which snaps over the key lock and it may come off with the dashboard. Once the dashboard is reinstalled simply snap it back in. Once all the clips have released pull the top of the dashboard toward you carefully so the four-way flasher switch on the upper right of the cluster is clear of the top of the dash. Squeeze the clip and remove the plug from the back of the switch. This done, the whole dashboard can be removed carefully from the car. It is long and flimsy.

6. There are four screws holding the exposed instrument cluster in place. Remove them and pull the cluster gently towards the steering wheel exposing the single wiring harness plugged into the top right of the cluster. Squeeze the single tab on the plug fully and pull it out of the cluster. Remove the cluster fully from the dash.
 
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