2005 Aztek HVAC Climate Controls Not Working

bpopilek

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Hello everyone! So I am having some issues with a 2005 Aztek that I'm trying to get 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. Before I parked the car this past winter, I was having 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!
 

melsg5

Staff member
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the link below provides wiring diagrams for the HVAV system.
do you have the owners manual which lists the fuses and relays?
you can not install a BCM from another vehicle without programming the unit.
 

bpopilek

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Thank you for the schematic. 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.

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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