I own a 1989 vette and the COOL button won't turn the interior temperature down, but the WARM button works. When I depress the COOL button, I can see a little orange (ish) light come on in the back ground.

Any ideas why depressing the COOL button doesn't reduce the temperature?

Thanks

 

electronic temp control?
If your sure the a/c compressor is running and the clutch is engaged and there is enough freon,
there is a device that they call a programmer under the dash down by the top of the gas pedal.
it's held on by a (in my case) a 9/32 head sheetmetal screw/bolt and it has the little solenoids that port the vacuum different places , like heater valve shut off, and vent door vacuum actuators and heater valve shut off etc.
check to see the vacuum block is still plugged into it and if it is, remove the programmer and see if it's burned up. there are resistors on the circuit card that im not sure, but I think control the blower motor speed too

the vacuum hoses might be split. when you turn it over you will see them.
vacuum pulls the heater valve closed. If you have a leak or the programmer isn't holding vacuum, the heater valve moves towards open with manifold vacuum falling off when you give it gas to accelerate.
it's possible the A/C fuse is blown, it's in the r/h door jamb and it's a large current limiter. there's also a control fuse too.
also it could be a grounding issue too.
do your temp numbers change with the blue button like they should?? it could be the control head also.
on my car, the red button moves the digital temp up and the blue button makes the temp numbers go down.
at 60 degrees, the compressor will stop going off and on to try to regulate the temp according to the temp selected, just stays on, and the fan kicks up a notch.
not sure where the compressor clutch relay is, but you should hear the clutch and relay click on and off with the key if the AC is on before you start the car.

 

I have a digital temp. readout and it is stuck on 90 because the COOL button won't reduce the interior temp. When I depress the COOL button it doesn't move to 85 degrees, then 84, then 83 (As you probably know, temps. between 86 - 89 don't show up)

Any Ideas......

 

I'm pretty sure that the buttons are not making contact inside the control head. I have to push my "off" button really hard to turn the unit off. Maybe there are some dirty contacts or weak springs behind those buttons.

 

How do I get to this area to clean and inspect the contacts

Thanks

 

Remove the left side dash trim around the cluster. Remove the center dash trim. Remove the screws around the climate control and unplug the harness. Pop the front off and remove the circuit board. Cleaning the contacts on the board where it connects to the front display/button box usually clears up an intermittent display or blinking lights issue. The contacts are easily cleaned with an eraser and alcohol. However, the button issue most likely lies withing the display/button box and I have never ventured into that. I think that there are plastic studs with "mushroomed" heads that must be removed to take this apart. Then springs might fly and it may never go back together. Maybe some can enlighten us as I would like this bit of information as well.

 

Don't use an eraser on gold or silver plated circuit board pads!!!! Its best to use electrical contact spray cleaner and a Q tip on the pins of the plug from the wiring harness. Push on the two sides at the rear of the control to release the circuit board and pull it forward. Then you can clean the contacts that make connection to the circuit board pads. Put it back together and try it out. If you still don't have the down temp function, then the circuit board has to be taken further apart and the board inspected to see if the carbon traces on the board behind the push button need repainting or if the circuit board solder joints need reflow (resoldering). If you don't have experience with circuit board repair, then leave it to someone who does. I don't know if the cluster repair centers work on climate control or not.