PCM, is it or isn't it the cause

FGirdich

Member
1998 century, the fans are not working, the AC clutch is not engaging. All fuses have checked sat, relays working properly, when a temp 12 volts are supplied to the fans and AC clutch, they work. I think the PCM is working because the car runs fine, idles fine, no service engine light, and the reference voltage going to the A/C refrigerent pressure sensor read 6 volts with an analog meter. I am really stumped. Can the data link from the HAVC have something to do with it? The blower and in car temperature controls all work with exception of the AC energizing. The only other things I have not checked are the pressure in the AC system and the engine coolant temperature sensor. Any thoughts would be greatly appreciated.
 

guyopel

Active Member
You will need to check the A/C pressures , the PCM will not turn on the A/C compressor if sys. is low ( to protect the compressor ) A code will be set ( no SES light because this does not affect emissions ) and will need to be cleared to charge the A/C sys. HTH
 

FGirdich

Member
Pcm

Yes I still need to do that, but I removed the AC refrigerent pressure sensor switch, used the paper clip method, and the AC compressor still did not engage. But shouldn't the fans still turn on based on engine temperature? I have not checked the resistance from the engine coolant temperature sensor
 
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