A/C works on 'high' only???

[Ryan G]

Anyone know what would cause my A/C to work only on the 'high' setting? I had just turned on my truck after being parked at work for hours, turned on my A/C (circulation... not the outside/ fresh air setting) and less that 30 seconds later, it just turned off. I didn't hear a click or anything like that. Anyone know what it could be and how to fix it? :banghead:



Thanks in advance!!!

 

[Bob McDonald]

It sounds like you have some resister issues. Here's how I think it works. I say 'think' because, while I 'know' it works this way on my wife's Grand Prix, I only recall previous threads on this board talking about about the circuit and they seemed to say it was the same.



When the switch is on high, the power (voltage) goes directly to the blower motor as it is only a single speed motor. When the switch is set to anyone of the other settings, a resister is inserted into the circuit that reduces the voltage to the motor, resulting in a slower speed.



So, if I am correct (and I am sure I will be corrected if not), there appears to be some problems with the resistor pack. So, where is it? The previous thread seemed to say is was accessible from the engine compartment near the firewall on the passenger side. Isn't that where the heater blower is mounted? I hope it is. Is was a real PITA to replace it on the Grand Prix as it was tucked up under the dash on the passenger side.



Good luck and let us know how it goes.

 

[Richard L]

I think Uncle Bob is correct. There is a resistor module that controls the various AC/Heater/Vent fan speeds.



It could also be a vaccum operated door leak controlled by the MAX AC setting. On some vehicles, when the AC placed in the MAX position, vaccum operated doors switch to use only recirculated air, and they have an electrical switch attached that kicks the fan onto high. If there is a failure like a vaccum leak, that door may close and force your AC into MAX cool mode???



Check and see if you can control your fan speeds in any other heat or vent postitions. If you can control the fan speeds in other settings, then the fan resistor is working fine, and your problem is with a vaccum door in the air box or the dash control.



...Rich

 

[Ryan G]

Thank you both for your input! You were both correct!!! I tried the steps that Richard told me to do and sure enough, the A/C only worked in the 'high' speed on all of the other settings. So I went out and bought a resistor, replaced it and celebrated!! Like Uncle Bob said, it was definitely a P.I.T.A. but well worth it in this hot Florida sun! Thanks again!!



Unfortunately, I didn't take pictures of the steps on what to do to replace the A/C resistor because I was trying to get it done before it got dark out. But I will try to find similar pictures to post on the "Projects" board for others to know. Had to take out the air box, then coolant/washer fluid bottle and reach down to get to it. Definitely a P.I.T.A.!!