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Author Topic: 2005 Aztek HVAC Climate Controls Not Working  (Read 89 times)
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BPopilek
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« on: July 08, 2019, 10:02:33 AM »

Hello everyone! So I am still having issues with a 2005 Aztek that I had posted about previously in the forums last year. I was never able to fully resolve the problems then, and because winter was around the corner, I just ended up buying my daughter another car and parking this one.  I'm now trying to get this Aztek running and working 100% so I can donate it to a friend that is disabled and needs a dependable car. Mechanically it is still working great, but electrically, not so much.

During my previous post, I had an issue where the BCM kept blowing fuses and the vehicle had intermittent HVAC controls. I have a strong feeling that these two problems are interconnected. Where I am at now is that my BCM is strangely no longer blowing fuses. Additionally, I have checked every last fuse in the car and they all tested good. However, I am no longer able to get any part of the HVAC system to work. The blower will not come on at all, and using a multimeter shows that I am not getting power down to the blower motor resistor pack. So the resistor and blower motor themselves appear to be good. Lastly, I just noticed today that pressing the AC and/or rear defrost buttons do nothing. The LED indicators that are part of the switches do not turn on when the buttons are pressed.

At this time, I have tried swapping out the climate control module with a spare that I picked up at the junk yard. This did nothing and I still have the same problem. Next I tried swapping the BCM I picked up for the same Aztek, and I still get nothing. The BCM from both the donor and original vehicles had the same base options, so I felt confident in choosing that particular one. The car starts and runs fine on both the original and replacement BCMs. The only thing that I noticed out of sorts with the second BCM unit installed is that the radio doesn't work and I now have a faulty airbag light that was not present with my original unit.

Does anyone know if this donor BCM needs to be reprogrammed by the dealer before the HVAC will work? Or does lack of programming just primarily cause the radio and airbag to be non-functional? Are there any other ideas that I might have overlooked about where I should be checking? Could it be a bad relay or something completely different? I'm open to any and all suggestions. Thanks for reading!
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Pontiac6KSTEAWD
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« Reply #1 on: July 08, 2019, 04:47:22 PM »

The BCM will likely need to be reprogrammed, as the BUS system is also checking for a VIN that it currently has a mismatch for. If you are going to get a reprogram, might as well as just get a new BCM, to alleviate any future problems.

As for the blower motor, that is really weird. Is there power getting to the HVAC controller?
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Brian - Carpe Diem

01 Pontiac Aztek GT OPT AWD 121k - 04 GMC Envoy XUV 182k - 05 Mercury Montego Premier AWD 52k (wrecked)

BPopilek
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« Reply #2 on: July 09, 2019, 02:40:36 PM »

As for the blower motor, that is really weird. Is there power getting to the HVAC controller?

I know I am getting power to the lights inside the HVAC control unit, but I'm unsure about the power going into the actual circuit control board. Is there a wiring diagram that anyone has that I can try checking my car against? I know that the fuses are all testing good, both inside the car and under the hood. And I picked up the used BCM just to test to see if it was related to the HVAC not working. If I have to replace it and have it programmed, then I'll definitely be looking for a new one to get programmed.
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BPopilek
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« Reply #3 on: Today at 10:00:21 AM »

I did find some HVAC schematics for this vehicle, but I'm not totally sure what I am looking at with them. I did some more testing and did discover some new info on this. With the vehicle running, I get no power to the following fuses:

21 - Rear Defogger
25 - Climate Control Blower Motor
26 - Climate Control Mode and Temperature Motors and Head-Up Display

Additionally the Rear Defogger Relay (20) is not being energized. If I take the cover off of this relay and force it closed, I then see power across fuse 21.

I did go back to using the stock original BCM and see no other issues with the vehicle except for this HVAC problem.

So I need to figure out where the power for this system is fed from so I can hopefully trace the wire back to find the problem. I suspect there was a dead short someplace or there is a fusible link that maybe blew? No idea at this point, and I would appreciate any further advice.Thank you!
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