Vent selector and a/c switches not working


NHRA427
12-02-2004, 07:12 PM
I have a 98 tahoe. The vent selector to get air to the defrost and vents doesnt work. It will only blow air out the floor duct. The a/c wont come on. The recirc button wont work. If i turn the fan switch off the a/c light will come on but as soon as i turn on the fan the a/c light goes off. the fan speed works and the rear defrost works , nothing else does. HELP

rrousou
12-07-2004, 02:16 PM
check the vacuum hose connections under the dash from the vent control to the servos would be a place to start

Notor1us
01-20-2005, 02:49 PM
I have a 98 tahoe. The vent selector to get air to the defrost and vents doesnt work. It will only blow air out the floor duct. The a/c wont come on. The recirc button wont work. If i turn the fan switch off the a/c light will come on but as soon as i turn on the fan the a/c light goes off. the fan speed works and the rear defrost works , nothing else does. HELP


someone please help i have the same problems and i know a couple other people on this board do too....

audio112
01-31-2005, 05:06 PM
well the 96 and newer do not have vacuum lines fpo the vent dampers the control the the direction where the air is sent it is electricial controled . the reason i know is that i have the same problem and still havent found out whats wrong yet . so what i did was found the the actuator next to the gas peddle and un pluged it and then cut the white wire not to close to the the plug . Then run a wire from a 3 way switch to that white wire , then u need a ground and a ignition under the dash at the column fuse that wire at the column . then after u do all that u have control from the floor / dash / and the deforst . Thats what i did for the time being untill someone finds the answer to is problem that we are having .

jtrevill
04-15-2005, 10:59 AM
I know this is an old thread, but has anyone in here with this problem gotten it resolved? I'm experiencing this as well.

Thanks!

Jason

NHRA427
04-15-2005, 08:48 PM
Yes i got mine fixed. It was the heating selector panel in the dash. I just went to chevy and bought another one. i paid 130.00 for it and it fixed everything. Its easy to replace. just pop the plastic face off the dash and it will pull out and replace.

audio112
04-18-2005, 01:58 PM
i did the samething replaced it abt 2 hours later it went up in smoke just like the first one and still can figure out why , was wondering if u had the same problem

jtrevill
04-18-2005, 02:17 PM
Thanks! I've got one on order now...

jtrevill
05-11-2005, 12:30 PM
I ordered a replacement, but it arrived DOA. I'm expecting a replacement soon. Hopefully it resolves the problem - it's getting hot out here! :)

BIG350tahoe98
05-16-2005, 10:25 PM
i did the samething replaced it abt 2 hours later it went up in smoke just like the first one and still can figure out why , was wondering if u had the same problem

I bought a 1998 tahoe about a month ago and the person I bought it from said something about how he had just replaced the a/c controll unit thing and now it just went out again yesterday. It did the same thing all of you said yours did where it only blows warm oir out the floor fents and nothing works right except for the rear defrost button. I was wondering if you (audio112) ever found out why your a/c controll unit went bad again. I dont know what to do, please help.
~Kevin

Imcgyver
07-31-2005, 04:53 PM
There are some likages under the dash that can fall off I have had it happen a few times if you can get underneth the carpet (thats where the parts fall too) you are looking for 2 rectangle rings with swival ends, 2 plastic pieces with slots on each end and a spring, put it all back togather probmem solved, it only can go back togather one way easy to figure out.

harborview
07-31-2005, 11:42 PM
If you've already replaced the panel that controls your fans, a/c etc.(you have to buy the whole unit from the dealer) and still having problems, you probably need a resistor. About $20 and has coils on it. you can do it yourself. take off the glove box and you'll find two screws on the top of the black unit (it will take a small socket set as there is not much headroom). Unplug the wiring harness out the top of it before you unscrew the thing. It also helps to take the screw, facing you, off first.

Just replace the unit and you should be back in business.

I replaced my fan switch console two months ago and three days ago I cranked the car up and had no fan out of the front vents. It was 103 deg this day. Thought it was the switch again because I got it to intermittently come on if switched to high. replaced switch and still nothing. found out a resistor could be bad. replaced myself with no problems thus far....relating to this.

Bodyshield
08-16-2005, 07:48 PM
mine had the same problem, you can just replace the whole "controlling" unit, you can buy it from AC Delco for about 80 bucks (thats how much i paid), and that fixed the problem, i had the exact same problems as listed as about, it fixed the problems

bsweasel
04-19-2006, 08:59 PM
I was having similar issues on my 96 Tahoe. I started at the actuator by the gas pedal as mentioned previously in the thread.

Upon inspection, way up under the dash above the actuator, I found the linkage connection at the top gate that opens/blocks the defroster vents was bound because the gate was out of place. I unhooked the linkage and moved the gate with my fingers using the small lever that the linkage connects to. By doing this, I was able to re-align the gate inside the vents and get it back into place so it opened and closed freely by hand.

Not 100% sure this was the only problem I decided to do some more testing. My first test was to find out what the 3 wires that connect to the actuator are. If you unplug the actuator, you will see that the 3 wires are in a 10 pin connector.

Pin 10 (white wire I think) is constant 12v dc (with the ignition on).

Pin 8 (Brown wire?) is 0v dc when the control knob is at one extreme. 6v DC in the middle vent position and 12v DC at the other extreme. Sorry I don't remember if the 12v is Defrost or Floor setting, I'm writing this from memory.

You can test if your controls work by connecting a meter to pin 8 and monitor the voltage as you move the switch to each position.

Pin 7 (Black Wire) is ground.

If get the same results as me, you can assume your control is ok and don't have to go spend the $130+ bucks (or more) on a new control unit only to find out its something else.

My next test was to remove the actuator and make sure it moved freely without any load on it. There are 2 socket screws (I think 7/32 socket, again memory not that great) that hold it in place. Remove both of them and pull it straight out toward the driver side. Plug in the 3 wire connector and move the control switch, you should see it turn freely from one position to the next. I didn't measure the range of movement but, its pretty obvious that it turns the same distance in both directions if it works properly.

Final result, once the gate moved freely, I reconnected the linkage, and re-attached the actuator to the linkage, and all was well with my vent system again. Hope this helps.

-Brad

Add your comment to this topic!