Aux Blower Motor Intermittent


New Member
Hey all, first timer here. Got a problem with the rear A/C blower only working when it feels like it. Sometimes it won't turn on no matter if using the front or rear controls I've read several other threads on the Trailblazer EXT auxiliary blower motor control module and feel pretty confident that it's the problem, but wanted to double-check that I'm not missing something before I buy a $90 piece of plastic and spend hours sweating and cursing the limited space I'll have to work with.

Also, and this is just a hypothetical. Would it be worth buying all new electrical components (actuators, blower motor, control module, resistors, etc.) and replacing everything at once? Or is it a waste of time and money in the false hope of getting another 14 years of problem-free HVAC service?



I never used the rear HVAC at all when I had my EXT. The rear A/C lines were blocked off, the actuators were both dead and the blower had a mind of its own, like yours. I pulled the fuse and never looked back.


Well-Known Member
A friend of mine is going through the same situation, auxiliary blower having a mind of it's own.

I have a spare resistor pack for it and will try to swap it for him tomorrow. I'll see how it goes and report back.


New Member
Mooseman, Hobby

Thanks, I hate just throwing money at the problem, but with the unnecessary complexity GM added to the HVAC system in these trucks it just seems unavoidable. Funny how the HVAC on a 2006 model truck needs a refresh before my '79 F-150 needs one...


Silver Supporter
Here's a link to a thread where another member was having an issue with his blower slowly starting.

I would almost guarantee it's the blower motor resistor. I put a few videos in that other post to help troubleshoot the issue if you don't want to just shoot the parts cannon at the problem.

When you buy those parts... especially that resistor, make sure it's an acdelco, bosche, or Delphi part. I usually just buy the parts from the junkyard if that part fixed the issue, then I'll buy the acdelco part online. That way I have a working backup part.
Last edited:


Well-Known Member
@Maverick6587, You're solving another thread here, the situation in this thread is that the rear A/C blower motor has a mind of its own, going on and off randomly (except when it's manually turned off).

That was a different thread that talked about slowly starting/stopping front blower motor.

@jonest3, I haven't had a chance to meet with him yet, so it might be q couple of days for me to return with results.

However, I do believe it's the rear resistor pack part # ACDelco 15-72813

Online statistics

Members online
Guests online
Total visitors

Forum statistics

Unanswered questions
Answered questions
Latest member
Top Bottom