AC won't turn off

Denbob55 · Post by **Denbob55** » Sun Jan 26, 2025 4:47 pm

I'm doing some pre-season maintenance. I noticed the A/C evaporator (?) is always frosted whether the A/C is off or not. Don't know anything about it, so what is not working here? thanks

svo413 · Post by **svo413** » Mon Jan 27, 2025 1:42 am

The compressor should run only on demand. Demand can be one of 2 ways. First is ac selected on the HVAC panel. There is a switch on the back of the HVAC panel to send 12 volts to the compressor through the pressure switch on the filter dryer up by the firewall. Low freon pressure cuts out the signal.

Second way for it to run is the HVAC selector in Defrost. This provides dryer air to the windshield regardless to what the temperature setting is on.

You should see the AC compressor engage when running as the end of the compressor will spin when the clutch gets 12 volts. The belt and pully will always spin ac or no ac. Just follow the ac lines and you will find the compressor mounted on top of the power steering pump.

ChuckG · Post by **ChuckG** » Thu Jan 30, 2025 8:34 am

Sounds like a failed switch, if the AC is not engaged as described above.

A qualified HVAC guy should be able to spot the problem quickly. That may be more economical than throwing parts at the problem.