Where do I find the problem w/ my heater & a/c control?

[shellylay81]

I've replaced my heater/ ac control twice. It either blows full blast, or NOT at all, again. I heard there was a computer board or something on the passengers side, but where is it exactly? And where can I find the replacement.. if thats even the problem. Will it remedy the problem? Or will I have to go and buy another control unit afterwards? This is getting ridiculous. My ac compressor just went out too. GRR. My tahoe is very expensive to own.

[MT-2500]

Originally Posted by shellylay81

I've replaced my heater/ ac control twice. It either blows full blast, or NOT at all, again. I heard there was a computer board or something on the passengers side, but where is it exactly? And where can I find the replacement.. if thats even the problem. Will it remedy the problem? Or will I have to go and buy another control unit afterwards? This is getting ridiculous. My ac compressor just went out too. GRR. My tahoe is very expensive to own.

We need more info.
Year and auto or manual AC/heater controls?
If the only problem is the heater blower/fan controls only blowing on high I would check the blower resister or fan switch and wiring and fuses.
If auto controls it could be shut down id ac compressor is bad or low on R-134 gas AC gas.

[shellylay81]

Originally Posted by MT-2500

We need more info.
Year and auto or manual AC/heater controls?
If the only problem is the heater blower/fan controls only blowing on high I would check the blower resister or fan switch and wiring and fuses.
If auto controls it could be shut down id ac compressor is bad or low on R-134 gas AC gas.

Its a 1996 Chevy Tahoe 5.7L Automatic, with Manual heater/ac controls. I have no a/c compressor right now, I am using a bypass pulley until my new compressor comes in. I had to order it online. I'm on my second manual control unit, and about to be on my third if this one is messed up. I know there is a circuit board somewhere on the passengers side, *someone in a previous thread mentioned that is why they all go bad*, but I can't find the thread now and I need to know where that circuit board is so I can repair or replace it. Also, If a replacement is needed, I need to know where I can find one at a decent price. Thanks.

Shelly

[MT-2500]

No circuit board on passengers side.
But check blower motor resistor on passenger side on heater housing.
MT

[777stickman]

Shelly:

The circuit board that you've mentioned is probably the "blower motor resistor" that MT is refering to. It controls the blower speeds thru resistors for settings other than HI. It's located about 2 feet towards the center from the passenger door on top of the heater "plenum". Look for a connector with these wires in it.

Yellow, Tan, Lt Blue & Drk Blue.

This is under the right side of the dash and you may have to remove the glove box for good access.

Most Auto parts stores should carry this....................Steve

[shellylay81]

Thank ya'll so much!! Do you think this will correct the problem I'm having with my existing heater/ac control unit.. ya know, the thing with the knobs? Or will I have to replace it again because of the bad resistor? Thanks. !! I'm taking this thread to the auto parts place to make sure I get the right item. Here's hoping to a resolution!

[shellylay81]

why is it every time I add one from the advance autoparts website to my cart, it says ignition blower motor resistor? Is that the same thing? It says a/c before I add it, then after it switches to "ignition blower motor resistor".. any help would be greatly appreciated, I'm trying to buy all this stuf before my fiance gets back so it will be a easy fix.

[777stickman]

Originally Posted by shellylay81

why is it every time I add one from the advance autoparts website to my cart, it says ignition blower motor resistor? Is that the same thing? It says a/c before I add it, then after it switches to "ignition blower motor resistor".. any help would be greatly appreciated, I'm trying to buy all this stuf before my fiance gets back so it will be a easy fix.

Shelly: There's never a real easy fix unless there is troubleshooting involved. In your case someone with electrical experience needs to check the blower resistor pack to confirm that it's either good or bad before buying a new one. It could be the blower motor relay, it could be wiring or the plugs the wiring goes into. From your previous posts I can be pretty certain that it's not the blower motor, it's not fuses and it's not the contol panel that you've replaced twice. As far as "ignition blower motor resistor" on-line. It's probably the right thing but keep in mind that most electrical parts are non-returnable..........Steve

[itsagaas]

Shelly,
I am having the exact same problem with my 1996 Tahoe. I have replaced the heater/AC control head (in the dash) a few times. The new ones always work then only work on High then not at all. The current one has been running on high ONLY for a few months. I have already replaced the blower resistor network, the blower motor and the relay on top of the blower motor housing. Did you ultimately fix the problem with your Tahoe to complete satisfaction? If so, what fix worked for you?
Thanks,
Ken

[mechanicswife]

My 99 Tahoe also has a problem with the A/C and heater fan. Tahoe has manual heater/AC. First the A/C started blowing not so cold air but it was winter so not a hugh deal. I planned to get it charged, but then the fan stopped working at all. My husband replaced the fan speed switch because sometimes it would not work when moving to a higher speed, but would work when slight pressure was applied towards the lower setting. He checked the fuses under the hood and on the drivers side. All good. He tested the blower fan which works when current is applied directly. The relay tested ok on all contacts and replacing the resistor (thing with 4 coils on it, in case my terminology is wrong) did not fix it. So the question is, where do we go from there. Since the A/C is not working, can this prevent the fan blower for the heater from working as well? It seems that the fan would come on and blow air from the heater or inside air when the ignition is turned on at least. Thanks so much for any help.

[jrbueiz]

Here's a thread I have started with the same problem some of you are having:
THREAD


Has anyone ever permanently fixed their problem with the A/C Heater Controller going out?

Those of you who have the problem and have been replacing the A/C Heater Controller; do you leave the A/C turned on when you turn the truck off and leave it on so that when you go to start the truck the A/C is already on?

I'm trying to narrow down if never switching the A/C Controller off is the problem we're having. If you visit my thread I say that others on other forums have mentioned that leaving the A/C on and not switching it off before restarting the truck can send an electrical spike to the controller at start up frying some if not all of the microprocessors in the unit.