A/C Clutch Cycle Switch On/Off Specs?? - #15-5715

[blk95lumina]

2000 Silverado LS RCSB w/ 5.3L and Harrison compressor

Just replaced all A/C components except for the evaporator and hard lines which were flushed. The compressor is cutting Off / On at higher pressures than what I expect. New low pressure switch is the GM AC clutch cycle switch part# 15-5715. Compressor is cutting off at ~29psi and kicking back on ~55psi, as tested with the vents on the lowest speed setting. When testing with the vents blowing on high the low side pressure maintains 40psi at 75F ambient.

I called AC Delco and dealerships and no one has the specs. Four Seasons switch (37308) lists their spec as Off 25psi and On 44psi, which is more in line with what I would expect. Maybe GM changed the spec to counter the slugging that happens with these low mount compressors?? Or maybe they boxed the wrong part?? I threw away the original pressure switch from 2000 but did notice while replacing the longer part# scribed/engraved on the body did not match the part# on the body of the new switch.

What are the low pressure Off and On specs for the GM AC clutch cycle switch part# 15-5715?

Thanks.

[blk95lumina]

Still cannot find the Off/On specs for 15-5715 so I went ahead and swapped in a Santech MT0968 which has the specs of Off: 1.8kg/cm or ~25psi and On: 2.8kg/cm or ~40psi. As mentioned the AC-Delco was disengaging the compressor clutch at ~30psi and by going ~5psi lower with the Santech switch the vent air temperature is blowing ~5 degrees F colder (~40F vs ~45F). This Santech switch has a green ring whereas the AC Delco has a brown ring, so maybe that indicates the Off/On pressure specs.

I also noticed that when the blower is on the lowest setting of 1, the pressure will still reach ~55-60psi before the compressor clutch re-engages after an Off cycle but on speed setting 2 it re-engages at ~40-45psi as expected. I checked the low and high pressures while testing and the high pressure was ~150psi, so no where near the high pressure cut off. My guess is that with the blower speed on 1 the compressor re-engages based on a timer rather than pressure as it does not behave this way on any other fan speed setting.

In all I feel better about using the Santech low pressure / clutch cycle switch as my vent temps are now blowing ~5 degrees cooler and the delay to come back on seemed to be related to fan speed as the low pressure would reach ~55-60psi with either the AC Delco or the Santech before kicking back on with the fan setting on 1.

System pressures when blower on highest setting of 5 are...
42psi Low / 210psi Hi at 80F ambient intake temp

[Blue Bowtie]

As long as the evap doesn't frost over it could be O.K. to push the gas temperature into the 30's. Either GM consolidated some part numbers or changed suppliers, but a different part number usually means some difference.

[j cAT]

the low pressure switch is 20-25psi switch opens then turns on around 40-45psi. so when you put the low /high gauges on your ac system open the doors air temp 80 degrees fan on max then the low pressure is 40-45 psi the high pressure is 275-300 psi.... you should also replace the belt tension -er on the compressor .. spring wears out if the compressor slugs then the tension-er will get damaged..old truck I had to replace my tension-er ..made tweet noises ac on..spring worn..