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2004 chevy trailblazer_lt_ext
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7 Posts
Discussion Starter #1
Maybe something was lost in translation from the manual to my head but I am not even sure how/when the rear blower is supposed to kick on. And also which vents the air should be coming out of in the 2nd and 3rd rows.

2004 TB EXT LS with 'manual' climate control.

I think when the dial on the console by the shifter is on 'R' then the rear blower and vent choice should be controlled by the controls on the back of the console. If that is true then I have a problem, the controls in the 2nd row don't seem to ever have any effect on the blower or the vent choice.

The front controls seem to work as they should:
passenger temp selector controls temperature for the back seats.
dial by the shifter controls rear fan speed (except R).
front vent selector also controls the rear vents that are open.

I've done no troubleshhoting since I'm not even sure if there is a problem. I even remeber years ago reading a TSB that explained the proper operation of the rear blower on an EXT because the manual wasn't clear and dealers were attampting repairs on vehicles that had no problems. I can't locate that TSB now.
 

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2003 gmc envoy_sle_xl
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193 Posts
Rear blower control

I have an 03 Envoy XL and the rear controls are on a black dial near the shifter itself....not on the dash console like the radio etc. On my vehicle there is also a control unit on the back of the middle console that controls airflow.

If you find that this doesn't work....your rear actuator could be blown....it is a simple repair that I have done. Search on here and you will find a nice little diagram that Roadie uses to illustrate where this thing lives. You have to undo the rear passenger side molding (it just snaps back...be careful not to break off clips)....search a bit and you will see it. Good luck...this one is fairly straight forward.....
 

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2005 chevy
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6,469 Posts
You can control the rear fan speed, and the mode from the front. I haven't tried changing the temperature, cuz down here I rarely need to run the heater much. :bonk:

If you have the front fan speed set from 1-3, the rear system will blow from the roof vents if your front is set to the dash vents or bi-level with the floor. If you change the front system to defrost or floor, the rear will switch to the floor. If you set the rear to speed 3, and the front to speed 1, you'll be able to hear the difference (if everything is working properly)

If this part works, but the 2nd row controls do not do anything, then your harware behind the passenger side cargo panel is fine, the problem is more likely your control module in the 2nd row. When the parking lights are on, does the 2nd row module light up along with everything else? Or does it stay dark? Could be a connection issue, there's a wiring harness inside the console back there that it plugs into. That would be the easiest case scenario.
 

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2002 gmc envoy_sle_xl
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22 Posts
I have an 02 Envoy XL and the back seat controls attached at the back of the center console do nothing. When I use the R0123 knob located next to the shifter the rear blower will occasionally kick on. But when that knob is set to R the rear controls should be able to control the rear blower and they do NOTHING. I've replaced both actuators (seems the gears break on them) and still no rear controls work. And again the control by the shifter only occasionally decides to kick on the blower. What I am wondering is if there is a resistor/control module similar to what is under the glove box for the rear controls that needs to be replaced. I have researched and can't find anything. Any help to troubleshoot this issue is appreciated.
 

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2002 gmc envoy_sle_xl
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22 Posts
Ok, I figured out how the back air works and it makes ZERO sense. So I have to have the R0123 knob set in either 1, 2 or 3, Then the front zone control will actually activate the Actuator under the center console to open and close the rear vents. Yet the rear controls on the back of the center console still do absolutely nothing. Why are they even there or have I missed something? Setting the R0123 knob in R should in theory allow full controls for the back to work independently of the front controls but they don't.
 
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