A/C system pressures

[LEEVON]

'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.

[chebyshortbox65]

Any system i shoot for between 20-30 on the low side.not unusual for the compressor to cycle if the fans on also idle it up and see what tge low side goes down to if i remember it cuts out at 10 did you pull a vacume?also the orfice tube is diffrent between the two and a 134 speciffic condensor works better then the r12 one
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[gchemist]

If you build up too much pressure, the high pressure switch will cut off the clutch. Pressure builds up at low speeds or idle. The switches work in series. Check if you have power at the clutch. If so, then your switches are working. Make sure you have a good ground on the clutch wire.

[LEEVON]

No vacuum pulled, just winging it. I think my working was funky...the compressor is working and building adequate pressure it just does not cycle the clutch OFF unless I turn it off. Maybe not a problem? I'm just used to seeing them cycle when everything is working right.