02 EXT rear HVAC blowing out only from floor vents (no roof) and can't adjust temp

myxobolus

Original poster
Member
Mar 22, 2012
4
I have 2002 TB EXT LTZ with the extra heater in the back. It hasn't worked properly in some time. I only get air blowing out of the third row floor vent. I do not get any air blowing out of the roof vents when either using the front controls while having the fan control on 1, 2 or 3 or when I have it on "R" and use the rear control unit behind the middle console. Also, when I adjust the temperature with either the front or rear console unit, it does not change. It just blows ambient or possibly slightly warmer. It's apparent to me that the actuators are not moving but I'm not sure what is causing it. I tried replacing the two actuators (ACDelco 15-72811 ; controlling floor/roof vents and cold/heat) last fall and that didn't seem to fix it. I was wondering if it could possibly be the BCMP (ACDelco 15-72813) that could be causing the issues. (This following point may be irrelevant of my rear issue but I have heard the actuator in the center armrest console making noise from time to time but it was my understanding that that actuator only controlled the floor vents blowing out of the lower part of the armrest console into the middle row. It currently blows hot air so I'm assuming it still works or is stuck open.) Back to the rear heat issue....could a bad BCMP cause both of the rear actuators to not operate and/or is there an easy way to test it? Thanks in advance...
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Good troubleshooting so far. The module is certainly a suspect, or the wiring harness getting power to it. Swapping with a buddy is the fastest way if you know anybody from meets or from your neighborhood with the same long wheelbase vehicle. Otherwise, you need a voltmeter and the schematics and a big of electrical troubleshooting experience. We have manuals on the site with schematics if you're that person. Assume you already did the module reset fuse pull trick to make the actuators recalibrate themselves.
 

myxobolus

Original poster
Member
Mar 22, 2012
4
Yes, I did the fuse pull last year after installing the actuators (fuse 36 HVAC B, correct?). Unfortunately, I don't know anyone with a long wheelbase. I can grab the multimeter and give it a shot. I'll have to hunt down those schematics later tonight.
 

Iahawkeye

Member
Jan 24, 2012
52
myxobolus said:
Yes, I did the fuse pull last year after installing the actuators (fuse 36 HVAC B, correct?). Unfortunately, I don't know anyone with a long wheelbase. I can grab the multimeter and give it a shot. I'll have to hunt down those schematics later tonight.

I was just wondering if you had any luck tracking down your problem?

I am just starting to investigate my own problem which is very similar to yours. However, my problem seems to be more occaisional. Some times I will call for cold vent air out of the roof vents and it will blow, but then it seems to reset to the floor. (Cold air on the floor does not help with car sick kids).
 

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