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**LEEVON** · 05-19-2013, 03:57 PM

'87 Silverado, a/c history unknown. The system was empty (no charge), but closed and I found the compressor low pressure switch to be faulty. I replaced the switch and added 22oz. of R134a refrigerant. I didn't want to overcharge, so I went to the conservative side of the charts I could find. Problem is, I'm sure every system is different and I don't have a service manual.

Ambient temperature 85 degrees. A/C on max, idling at 1500rpm for 10 minutes, I'm getting low side pressure of of 40-45 and high side of 200-215. but the vent temperature is 60 degrees. I noticed the compressor clutch never cycled, idling or out driving. I'm thinking that can't be good! I wonder if the high pressure switch is bad or what?

What is the recommended pressure for this system? If I'm on the low side, should I add a few more ounces or assume that I have bigger problems like a clogged orifice tube, bad compresor or contaminated system? I'm hoping to limp it along until I have the time to go through everything but if adding a little more.

05-19-2013, 03:57 PM	#1
LEEVON Moderator Join Date: Jul 2006 Location: Ozark, MO Posts: 4,919	A/C system pressures '87 Silverado, a/c history unknown. The system was empty (no charge), but closed and I found the compressor low pressure switch to be faulty. I replaced the switch and added 22oz. of R134a refrigerant. I didn't want to overcharge, so I went to the conservative side of the charts I could find. Problem is, I'm sure every system is different and I don't have a service manual. Ambient temperature 85 degrees. A/C on max, idling at 1500rpm for 10 minutes, I'm getting low side pressure of of 40-45 and high side of 200-215. but the vent temperature is 60 degrees. I noticed the compressor clutch never cycled, idling or out driving. I'm thinking that can't be good! I wonder if the high pressure switch is bad or what? What is the recommended pressure for this system? If I'm on the low side, should I add a few more ounces or assume that I have bigger problems like a clogged orifice tube, bad compresor or contaminated system? I'm hoping to limp it along until I have the time to go through everything but if adding a little more. __________________ '86 GMC C30 Crew ~ '86 C20 Crew ~ '79 K15 Sierra Grande ~ '76 Blazer 2wd ~ '74K10 ~ '71 Cheyenne swb ~'50 3100 bagged ~ '80 Wife ~ Late model kids Last edited by LEEVON; 05-19-2013 at 04:24 PM.