ac and heater problems need help

[dbriana]

My ac worked fine couple of weeks ago, now it blows through the bottom heater vents and defroster vent when it is switched to ac. Plus the heater will not warm up, (turned up to 90) its like it stuck on ac but blows through bottom even though switch and lights cycle between air, heat, vent, fan speed increases up and down, compressor kicks on when turned on. I have noticed sometimes my outside tempature reading stays stuck on an earlier reading until i start next time and takes about 3 minutes to be correct, could this be related and finally caused this problem? Any ideas, TIA.

[Corvette95]

a factory service manual would help you a lot. The first thoughts is the ac control head....take it out, take it apart carefully and clean the contacts. It could be a blend door (not fun on a 90 the worst) or it could be the blower controller out on the firewall in front of the passenger side (inthe engine bay side -three seven mm screws) but before I take things apart, with a manual you can read what is happening thought the ac temp digital readout...thats the quickest and best way. Check out helms inc for manual or ebay...good luck

[Tom]

My 90 recently took to only blowing cold air. It would send the cold air through the correct oulet that corresponded to the button pushed but it would always be cold air no matter what the temperature setting. I looked in the shop manual and one of the first steps in troubleshooting the AC system was to remove the Courtesy and Radio fuses for a minimum of 15 seconds (with the car shut off) to reset the AC programmer. I pulled these two fuses and the AC fuse and my AC started working properly again. I would try pulling the fuses on your car.

The AC in my car occasionally quits responding to the buttons and they start working again after shutting the car off and then restarting the car. That didn't work in this case but pulling the fuses did.

[dbriana]

It turned out to be a vaccuum line that came unplugged under the right side dash.