pressure switch a/c

W:banghead: here exactly will I find the switch or are there more than 1? 1997 century,clutch does not engage. Has resistance across coil spades and refrigerant pressure is correct. Swapped out relay and checked diode, current only flows one way .
put 12 volts to compressor coil connection, started to melt plug in secnds, but clutch did kick in and comp. spun

Welcome to AF.

It would help to post what year Century you have.

1997 century,clutch does not engage.

Normally, the "Low Pressure" switch is mounted in the side of the accummulator (Drier Bottle).....The "High Side" switch is mounted in the rear of the AC-Compressor. AC-Delco's website is showing only 1 sensor, and it appears to be the one that's mounted in the rear of the AC-Compressor.

ACDelco Part # 15-5742 SENSOR,A/C REFRIG PRESS. Go to this link below, the type in 15-5742 . It will show a pic of it.

AC-Delco Part Image (http://198.208.187.182/internet/ViewPartImage.jsp)

The pic shows the one by the acumulator (hi side). On these type R134a AC systems I recall GM changed the way the refrigerant pressure switch works. It receives a 5 volt reference signal from the PCM module and sends a varying signal representive of the refrigerant pressure back. The PCM module uses it to control the turn on of the cooling fans when A/C is on.