DaveP85C4

I've never heard that switch called a "safety switch", probably because that's not what it is. I called it by its correct term: Clutch Cycling Switch. Get out your service manual and go to C60 "air conditioning". It calls this system a "Clutch Cycling Orfice Tube" system. CCOT.

Clutch CYCLING. The cycling switch's main function is to maintain as low as possible evaporator temperature without icing. The clutch turns off if pressure gets below the equivalent of 33deg F. About 28psi for R12, 22psi for R134. When pressure rises to about 40-42psi, the clutch re-engages, and draws the low side down again. Over and Over. Hence "Cycling". The evaporator thaws during the off cycles because its temperature rises above freezing.

If the compressor ran continuously under conditions where icing can occur, the evaporator would become solidly blocked by ice formation, airflow would stop, and there would be such low return flow volume to the compressor that it could become oil starved and damaged.

Thanks Roy for the support.

PatternDayTrader

A distinction without difference.

Go read through this thread

https://www.corvetteforum.com/forums...ol-issues.html

Then tell us how stupid we are and answer my question about the clutch cycling on the 94-95 cars. (if you have a service manual available).

Hot Rod Roy

This thread has a lot of good information, and also a lot of confusing information. Th OP has an '85, so all the stuff about automatic/computer controlled a/c's doesn't help the OP! His only question is "why does my fan run".

My post was an attempt to get back to basics, so the OP could filter out the info that doesn't apply to him. The high side pressure switch that controls his radiator fan is "normally open" (later automatic temp control cars are different), and several have stated correctly that switch may be his problem.

If anyone finds errors in my description of basic a/c operation, I'd like to know about it!