HVAC blower position switch problem

[DWC]

I have a '04 Chevy 2500HD truck (gas and LT pkg.). My blower/fan position switch is not working properly. No matter what position I have the switch pointed to, the air only comes out of the front dash vents. The air will not blow out of the defroster or footwell vents. I searched the forums and found numerous threads about problems/fixes for fan speed switches, but could not find a fix for the fan position switch.

 

Please advise.

 

Thanks,

 

Daniel

[ChevyTech007]

I would take it to a dealer and have it scanned for codes. Probably a mode door actuator. It could be the bulletin below.

 

Subject: HVAC System Cannot Be Controlled Or Defaults To Defrost Mode (Repair HVAC Actuator Harness) #04-01-38-008 - (06/17/2004)

 

 

 

Models: 2003-2005 Cadillac Escalade, Escalade ESV, Escalade EXT

 

2003-2005 Chevrolet Avalanche, Silverado, Suburban, Tahoe

 

2003-2005 GMC Sierra, Yukon, Yukon XL

 

 

 

 

--------------------------------------------------------------------------------

 

Condition

• Some customers may comment that they cannot control the HVAC (heating, ventilation and air conditioning) system. Others may comment that the HVAC system defaults to the Defrost mode.

 

• Technicians may find that the following diagnostic trouble codes have set:

 

• B0229 Recirculation Actuator

 

• B0414 Left Air Temperature Actuator

 

• B0424 Right Air Temperature Actuator

 

• B3770 Mode Actuator

 

Cause

The HVAC actuator harness may contact a sharp edge on the instrument panel support brace, causing a rub through condition and a ground out of the actuator control and/or feedback circuits.

 

Correction

 

 

 

 

Locate the HVAC actuator harness contact point shown by the arrow in the above illustration. The illustration is of the instrument panel with the instrument panel compartment door opened and folded downward. The actuator harness is located in the left side of the opening in the instrument panel.

 

Technicians are to inspect the HVAC actuator harness for contact with the instrument panel support brace. Repair any damage to the actuator harness wiring and install protective plastic conduit over the harness. Install friction tape over the sharp edge of the instrument panel brace. Clear the diagnostic trouble codes and verify proper HVAC system operation.

[DWC]

Thank you for the detailed response. I'll take it to the dealer and have them follow this procedure.

 

Thanks again,

 

Daniel

[DWC]

Well, first I removed the glove compartment and looked/felt all the wiring harnesses that I could access and none showed any signs of contact/rubbing. So then I went to the dealership and spoke with a technician and he said before I pay $77 to have them scan for codes I should unhook the pos. and neg. battery cables, touch them together for about 10 seconds and reattach. He claimed that this will clear any codes and may cause the problem to go away. I did this and it didn't help. He suggested that if this didn't work then most likely it's the mode door actuator. So, does anyone have a part # for this?

 

Thanks for your help,

 

Daniel

[DWC]

Anybody have any idea of the mode door actuator part #??

 

Daniel

[DWC]

I still haven't gotten this issue resolved. I also had another related issue the other day. Sometimes, if I start my truck and the HVAC system is completely off, once I turn the HVAC system on it blows hot air no matter what setting I have it on, A/C, defrost, whatever. Turning the HVAC system completely off and then back on does nothing either.

 

Please provide me with some feedback so I can remedy this issue.

 

Thanks,

 

Daniel C.

[mackskibum]

Look here....

 

http://www.gm-trucks.com/forums/index.php?showtopic=81984

 

Try the fuse method- it may work for you

[DWC]

Thanks for the response.

 

I'll give that a try and see what happens.

 

Daniel

[DWC]

Well I tried the fuse method with no luck. I still have no control over HVAC van position. How does the HVAC fan control work? Is there a gate/flap that controls the direction of airflow? If so, do those normally cause problems?

 

Thanks for any input,

 

Daniel

[cfeiring]

DWC

 

I am not a mechanic but a Paramedic / computer programmer.

But I had an ambulance last week with a similar problem --- It is a ford but might be similar solution

Our shop forman fixed the problem in about 20 mins start to finish.

I asked for the explanation as he repaired since I am trying to learn simple mechanical skills.

It was a loss of vacum. In the ford the actuator - flapper valve as a safety measure defaults to the deforst setting no matter what the settine for the postion of output of the fan is set to untill the vacum is restored.

The mechanic just pulled a new hose from the engine compartment thru the fire wall to the connector under the dash and it was fixed.

I would guess that the HVAC in a GM would operate in the same basic safety idea.

Like I said not a mechanic but maybe worth a look/try. I do not have any idea were to look on a GM....new to owning a GM always have had a Ford untill the start of July.

 

I hope this turns out to be a solution to your problem.

[DWC]

I still haven't gotten this issue resolved. I also had another related issue the other day. Sometimes, if I start my truck and the HVAC system is completely off, once I turn the HVAC system on it blows hot air no matter what setting I have it on, A/C, defrost, whatever. Turning the HVAC system completely off and then back on does nothing either.

 

Please provide me with some feedback so I can remedy this issue.

 

Well, I haven't been able to locate any vacuum leaks so far. But, yesterday I did notice something I hadn't before. When hot air blows, as in the situation described above, it was only blowing hot out of the 2 dash vents for the driver. The 2 passenger side dash vents were blowing cool, as they should. I just thought I would mention this in hopes that someone will say, "Oh, if it's doing that, then you just need to replace XXXXXXX, part # XXXXX

 

Any help appreciated,

 

Daniel

[VinceJE]

I know this is an old thread but my 02 GMC has a very similar problem that happens intermittently. Just thought I'd bump this thread to see if anyone found the issue & remedy.

 

THANKS!!