1999 Tahoe 5.7 L warm air from AC

[d_w79]

Was getting warmish air from (intermittently) from ac. Shop replaced Temp-Blend and Mode Door Actuators. Problem is still there and the air is a bit warmer than before! I don't know if they installed the parts correctly as I find hints on how the actuators must be installed/calibrated.

I think now that I have to remove the dash and find and fix the problem myself. Any instructions step by step on removing the dash?
Also, any other input on this chore will be greatly appreciated by this old tinkerer! Thanks. ...dw

 

[lesterl]

Make shure that the AC is running and cooling.

May have to check the control head.

IIRC there are 3 wires to the actuators, one will be ground, one will have 12v, the third wire (white?) will vary with each control (blend will go from high to low as the door should swing one way to the other.)

 

[d_w79]

Thanks Lester. I will start there. So I should check for good contact and ground?
Do you know if I can see the doors function from the floorboard?
Will post back asap. ...dw

 

[lesterl]

You can see the mode door one at the gas pedal move IIRC...

Checking the 12v and ground would be good, would also allow you to know the other wire that should vary and you can monitor with a meter and adjust your controls, you want to see a very linear, consistant voltage swing as you change the knob...

 

[d_w79]

OK thanks. I think I have to surrender and just call it my 'Winter' car. Spent the day trying to get the HVAC case screws out to check the actuator in there but looks like I'm just not quiet young as I used to be. ) ...dw

 

[lesterl]

The acuators are on the outside, should be pretty easy to get to, like 2 or 3 screws, dont even need to remove them, just probe with a meter....

 

[d_w79]

Appreciate your input Lester! I'm done with it! More than I can handle. I will post back if I find someone who wants to work on it. can't go back to the shop since They got $460 for nothing, it appears.
Thank You very much! ...dw

 

[lesterl]

OK.... let us know.... probably a bad actuator, I have a bad Recirc one, I just smash the dash with my fist because it is the hard one to get to....

 

[d_w79]

Well, here is my final stance, I guess. Was not able to get the HVAC case out but did get some of the screws replaced after trying.

I have faith in my shop owner's honesty but did the mechanic clean the doors and did they actually replace the 'blend door' actuator? I don't know! Of course they say yes. They saved two old actuarors for me.

Now, it seems that my only shot is to remove the dash and I have not found any specific directions how to do that so, it must be a bear too! Parts stores don't have it. ...dw

 

[d_w79]

Now this is really something! I just tried yet another search for 'Dash Removal' and it popped up on EHow!
http://www.ehow.com/how_7801718_install-dash-1999-chevy-tahoe.html

Definitely out of my league so I'll stop there. I didn't even have A/C in my first few cars, even the 1928 Model A ...dw

 

[lesterl]

The blend door is behind the glovebox IIRC.... Only need to remove dash to replace the Recirc actuator...

 

[d_w79]

UH-OH! My first move was to take out the glove box and check behind there. I could see just a bit of an Actuator to the left which put it over the HVAC Case and past some framework making it totally unreachable from the glove box.
I will look in there again-hope I just missed it! Will be a coupla days before I can do it. thnx. ...dw

 

[lesterl]

http://www.youtube.com/watch?v=Ow0OOfIFtlU

IIRC you can replace that sucker without ripping the dash out.... did it look new?

 

[d_w79]

BY golly I didn't look that hard! I will give it a good full inspection and see if I can figure it out or maybe even get a visual on the door to see if it is OK! Sure do appreciate your hanging in with me. Gonna try and make it pay off!
thnx Lester.

 

[lesterl]

No problem, would be great if you could find something.

I have never replaced an actuator (in a Tahoe), and as I understand it the one I need to replace is the PITA one on top of the HVAC unit. (Recirc.)

I did replace one inside a 1998 S10 Blazer and I had to pull the dash to do it... I actually pulled the thing apart and the main gear had split so I glued and used some wire to tie the gear together. Then my brother in law sold it (it was his truck).....

 

[d_w79]

Update: The Actuator is not new and has a different number than on my shop bill so it was not replaced. Searching shows it to be the 'main' one that I wanted replaced - the Heat/Blend. It is located behind the ashtray and
is partly visible from the glovebox - removed.

I stumbled upon a response by 'Piratelowrider' on GMC Forum. He said: You can reset the blend door calibration by pulling the HVAC fuse for about a minute, put the fuse back in and turn the key to on position. You should hear the doors moving and calibrating.

I followed that and the air was almost up to cold. Took about 50 miles intown and on freeway in 105 deg. desert and it performed the first time in a while. I now believe that I cut the calibration short so I Re-did it 5 min. with fuse out then 12 minutes of recal. time - I could barely hear some movement for 7minutes.
So, tomorrow I take it out and see where we are. Hoping the actuator is strong enough I won't have to give another bag of money to replace it!

Will report back tomorrow, good or not-so-good !! ...dw

 

[d_w79]

And the verdict is in!! The 5 minute 'Fuse Out' And the 12 minute 'Recalibrate' gave me back a Fully Cold A/C which I haven't had in at least a coupla years!!

I tried to register on GM Forum to give proper thanks and praise to 'piratelowrider' but that was more of a chore than working on my A/C

Thanks again Lester for prodding me along!

...dw

 

[d_w79]

To cap off this experience:

Now, I find it was more simple than i imagined. For my own satisfaction I searched 'Calibrate Actuators' and there is all I ever needed to know - just didn't know what words to Search!!
Now I know that all the shops I've been to knew or should have known how to fix it. This trip cost me $445 for nothing! The others probably twice that much.

Hopefully my bad experience will save others from the beating!!

Thanks again Lester! ...dw

 

[lesterl]

I dont know that there is a calibration for mine as it appears to be a simple analog system (control voltage is sent to actuator along with 12v power and wherever the control voltage goes the actuator follows.)

Yours must be controlled by a microcontroller, glad it worked for ya!