AC high pressure switch replacement

[Floyd1965]

I was diagnosing an inoperable rad fan on my 1993 Ciera 3.3 and the diagnostic chart I found online got me to test the AC pressure switches first. What I did was: took connector off of low pressure switch and installed a jumper, to no avail. Then i went underneath to the high pressure switch on the back of the compressor, took off the pigtail and put a jumper on it. Then I went back to the low pressure switch connector, put in the jumper, and lo and behold the compressor locked up, and the rad fan come on. I then took the jumper off of the low pressure connector, put it back on the switch, and retried the system. The compressor came on like normal. At that point I determined that the high pressure switch was faulty.

My question is: how hard is it and what do I have to do to replace the high pressure switch while the compressor is still installed on the vehicle? Do I have to get the refrigerant evacuated before changing the switch?

[86euro]

If the pressure switch is compressor mounted, then yes, the system needs evacuated. Then you remove the internal type snap ring and pull out the switch. If the system is in a vacuum from having the refrigerant removed, it might not come out very easy. Once it's out, you will replace the o-ring (should come with the new switch, along with a snap ring) and put a little A/C oil on it as a lubricant. Then install the new switch.