Rear HVAC vents not blowing

[ksimm92]

hey everyone, I joined a few months back, but this is the first thread I have started!


The issue I am having is when I try and turn on the rear HVAC vents nothing blows out (no heat or air conditioning). The power button does light up, just nothing blows out. I do remember using it when I first bought my truck (3 years ago) but I don't have passengers back there very often, but I know at some point it DID work.

Something i did notice was when moving the mode (high, low, or mixed) I can hear the actuator moving. I'm not sure if that would be related, just thought it would be worth mentioning.



My first thought was that if the light on the power button comes on, then it IS getting power... Does this mean the blower motor is bad?

I just thought I would ask before throwing parts at it.



Thanks in advance for any input!! GMTnation is the best!

 

[The_Roadie]

The airflow actuator's working proves the control module has power. Short wheelbase rear seat blower motors fail so seldom, I seem to remember only 2-3 in my entire time working with the platform. The blower is not in the center console, but at the extreme lower left of the center console, and it just blows through a plenum in the center console to the rear vents. But it does have a little resistor built in for the speed change, but if high speed is also dead, then it can't be the resistor. So that leaves the wiring harness to the motor, possibly a bad ground, or a bad motor. Take the trim off your center dash area and poke about in the harness to the motor with your meter. High speed wire is dark green. Medium speed power is dark blue, and black, as always, is ground.

 

[ksimm92]

The airflow actuator's working proves the control module has power. Short wheelbase rear seat blower motors fail so seldom, I seem to remember only 2-3 in my entire time working with the platform. The blower is not in the center console, but at the extreme lower left of the center console, and it just blows through a plenum in the center console to the rear vents. But it does have a little resistor built in for the speed change, but if high speed is also dead, then it can't be the resistor. So that leaves the wiring harness to the motor, possibly a bad ground, or a bad motor. Take the trim off your center dash area and poke about in the harness to the motor with your meter. High speed wire is dark green. Medium speed power is dark blue, and black, as always, is ground.

thanks roadie, I have a multi meter and pretty good with it. Ill take a look at the wires and see what I find.

 

[lovesrugers]

Something you may want to check before taking things apart is to see if you have the front defroster turned on. I am not sure which climate control set you have, my Bravada has the fully automatic. When I push the front defrost button it will stop the blower from working in the rear area. It will exhibit the exact symptoms you list as the problem as long as the front defroster is turned on. I believe I read in my manual that it does this on purpose or was designed to do this. If my son wants the rear blower to work I have to remember to set my controls to manual mode and then select front defrost with bottom vents. This will allow the rear blower to run.

I hope this helps you out. I know it drove me crazy trying to figure out why the rear blower was seeming to only work intermittently a few years ago.

Jerry