Automotive AC pressures question

[tinmanSC]

How much pressure is required to be in a system before the low pressure switch will allow the compressor to start? That is ,when the system is off (no low/high side) the system needs to be filled to X psi to allow the compressor to start.

Or is this only measured on the low side after the compressor has engaged?

 

[RF Overlord]

I'm sure it varies by manufacturer, but I seem to remember when my 2000 MGM was low on refrigerant, it would cycle the compressor off when the low side got to about 22 lbs and not turn back on until it was at about 45 lbs. YMMV

 

[Chris142]

Off @ 20ish. And on @ 40ish depending on the car

 

[tinmanSC]

thanks for the info. it really helped.