rear hvac and radio control not working

[jshinabery18]

Having a problem with any air flow coming from the rear vents as well as rear radio controls. I'll try too be thorough.

-The control unit has back lighting on the buttons, but no digital display. It does not respond to any buttons pressed, but when it is disconnected the rear speakers go out. I have tried another control unit with the same results.
-12v outlet works
-no airflow from rear vents with the front switch on any setting (R 0 1 2 3)
-checked fuse #36 and recalibrated vents. All front vents work fine.
I'm stuck, I thought the control unit was the only thing that made sense tying the two issues together, but no luck with a new one.. Any suggestions??

?anyone know what the VENT RELAY in the rear fuse panel is responsible for?
Thnks

 

[The_Roadie]

Welcome!

The 12V outlets are all separately fused and unrelated to the problem.

Can you confirm you really have a good ground on the module pin B16 - black, and 12V on A16, orange? Otherwise we have to dig deeper into the signals at each of the pins on that connector with your meter. Assume you have a meter?

In my 2004 shop manual, there is a relay in position #22 labeled RAP standing for "Retained Accessory Power" that's fed by fuse #20 labeled VENT WDO. Not sure if your relay has been renamed. In any event, RAP is a way for the vehicle to allow you to turn off the ignition switch, but it "retains" the ability (until you open a door) to raise the power windows, close the sunroof, and (through this relay) close the powered rear vent windows in the way back. Easiest way to prove this is to yank the relay and see if you lose that feature. Should be discussed in the owner's manual.

 

[jshinabery18]

Ok tried those suggestions. have good 12-13volts on the orange wire a16.
The Black b16 has good 0.00 continuity with key in off position, but goes up to .20 on 20k setting when the key is in run position.
Is that acceptable, or should I be reading 0.00 all of the time?
I even spliced in an extra ground line with some aligator clips from the seat mounting bolt and got the same readings.


P.s. Roadie. Right on the relay. the fuse box cover said vent relay next to the hole showing that relay.

 

[ramrod919]

Has anyone come up with a solution to this problem? I'm having the same issue. I did not have my meter handy today. I grabbed up my test light and have a good power on the orange pin. I will try to dig up my meter to check the ground. However, I think there is a slight difference in problems. I do not believe my control panel has backlighting. Any help is always greatly appreciated.

 

[The_Roadie]

I do not believe my control panel has backlighting.

All control panels have backlighting, but many of them use a separate dimmable lamp bus from the BCM to accomplish it. If your lamps are dark, it could be the wiring or the lamps. The schematics have a clue. Have you downloaded a set?

 

[ramrod919]

I'm sorry. What i meant is that I don't think my backlighting works either. And I verified that tonight. No lights came on.

Roadie, I have not downloaded a set.