A/C won't blow through dash vents...heater works

[jahworks123]

I have a strange problem with my 97 Tahoe. When you turn the A/C on, in will only blow to your feet or through the defront vents, it will NOT blow through the dash vent, regardless of the setting. Does anyone know what could cuase this problem? I was thinking of replacing the A/C Heater control unit, but I'd like to get some input before spending all the $$$ for trying to shot-gun a fix.

Thanks

PROBLEM SOLVED (8-22-06):

REPLACED THE HEATER / AC CONTROLLER WITH AC DELCO PART # 15-72547 (GM # 09378805) PURCHASED ON EBAY FOR $102.95 SHIPPED! Note: There are two types of similar controllers on EBAY. One is for trucks with rear defroster (leftmost button at the bottom)...the other is for trucks WITHOUT (no leftmost button). I could not tell from the EBAY pics, but the description confirmed that I got the one I needed. Make sure you get the right one.

Installation was simple. Only tool needed was a flat head screw driver.

Removed the trim panel (just pry it straight off towards you). I was able to leave all the buttons connected to the trim panel. I simply rotated the trim panel assembly couterclockswise, so I had enough room to work. (Note: The trim is connected to the shroud around the instrument cluster. It has to be pulled away enough to clear the top of the dash before it can be rotated). Once I had enough room to work, I pryed away the tabs that held the old controller in place (I used the new one as a guide so I knew where to place the flathead scredriver). Then, I removed the 3 connectors on the back of the old controller (need a screw driver to pry off at least one of those connectors). I'm gonna say one of the most dreaded sentences for the do-it-yourselfer...but it's true..installation is simply the reverse of removal. Plug the 3 connectors in, snap the controller back into place, snap the trip back into place, and enjoy the cold air in your face!

Thanks for all the suggestions I had while trying to figure this out. Hopefully it solved my intemittent non-working of my heater problem I have in winter also.

I hope this helps out someone who may have a similar problem.

1997 Tahoe 4WD

[2000CAYukon]

I have a 90 K1500 pickup. On mine when it did the same thing, it was the mode actuator. It was worn out and could not move the door to change from floor/defrost to vent.

On my 90, it was located above the tranny hump and under the dash near the gas pedal. I unscrewed it and then turned on the ignition. I could see it move but very slowly. A new one from ac delco (not a dealer) fixed the problem on mine.

//2000CAYukon

[driftkid21]

I had that problem with an S-10 i had. check your hoses that go to your vacuum thay may have just came loose,the vacuum I had was attached under the hood on the drivers side, it was a softball sized black ball, hope that helps

[swp5767]

Originally Posted by driftkid21

I had that problem with an S-10 i had. check your hoses that go to your vacuum thay may have just came loose,the vacuum I had was attached under the hood on the drivers side, it was a softball sized black ball, hope that helps

I had a similar issue with the wifes Astro. Fix the broken vacuum line and you should be set.

[jahworks123]

I forgot to mention that when the heat is on, it works fine. I can get heat to blow through whichever vents I select. So, that may perhaps rule out the acctuator?

Is the vacuum hose you guys are referring to a part of the general vacuum system on the truck? I do have some rough idling issues I'm trying to resolve, but I have not performed a vacuum test yet.

I will check to see if I can find the vacuum hoses that were mentioned. I'm consider myself mechanically inclined, but I admit I don't have a lot of experience with the truck.

Thanks for the feedback so far.

[2000CAYukon]

Originally Posted by jahworks123

I forgot to mention that when the heat is on, it works fine. I can get heat to blow through whichever vents I select. So, that may perhaps rule out the acctuator?

Thanks for the feedback so far.

If things work fine with the heat on, then the actuator or vacuum lines are not your issue. This sounds more like a bad controller to me.

//2000CAYukon

[swp5767]

[quote]
Is the vacuum hose you guys are referring to a part of the general vacuum system on the truck? I do have some rough idling issues I'm trying to resolve, but I have not performed a vacuum test yet.
[quote]

The vacuum lines I was refering to are very small, and there were a break, your engine probably wounldnt notice. On the Astro, you couldnt even hear the leak, but it was enough not to work the AC controls correctly.