LaszloP wrote:
There isn't a pressure switch on the compressor but there is a pressure switch on top of the drier. I didn't replace that one... wonder if that is the culprit?
Thank you for the prompt response.
GM P Series Chassis.
Odd, I usually have Too Much Coffee!
If you have the typical GM A/C system, it cycles only when the LOW side gets down into the low 20's of PSI. They're called Clutch Cycling Orifice Tube (CCOT) and the "Cycling" part's actually a little misleading, since it's NOT cycling to control cabin temperature like a system with a thermostat does. Temp is controlled with a Blend Door that mixes cold air from the A/C Evaporator Coil with hot air from the Heater Core.
A 1996 vehicle should be on a 1996 or possibly a 1995 chassis. Auto A/C was changed over from the R12 that was used when auto A/C started in the 1950's, to R134A that's supposedly more ozone-layer-safe.
Do you have any labeling telling if the original refrigerant in fact WAS R134A? I ask because of my personal experience with "retrofitted" auto A/C systems. They will not tolerate being overcharged. The high side goes crazy high and the compressor will balk. Chirping belts, slipping clutch, etc. etc. On a retrofitted RV we had, the charge had to be kept below specs to not balk the compressor. On a car I did, compressor would balk till I added an additional cooling fan on the condenser.
A proper retrofit should include addition of a high side cutoff switch, and as noted above, many compressors have a port for one. The GM HR6, DA6, HT6, have the ports, and come with a "slug" in the port for applications that don't call for the switch.
