The system was converted by the PO to r134. So I jump the switch and the compressor turned. Attached the manifold valves which registered 0 pressure both high and low So I vacuum for 1 hr. Then I close the manifold gauges and and 45 minutes later no leakage. So I recharge with 2 cans of Enviro-Safe and afterwards the gauges show 75 lbs. on both high and low side and no cooling. Does this mean I have a leak although the vacuum altough it showed a tight system? Or a bad compressor?

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As many on this forum will tell you, holding a vacuum for a period of time is no guarantee of a leak-free system when that system operates at pressures many times higher than one atmosphere.

Pressure is the only way to properly leak test. I learned this the difficult way...

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cbjukraine
'84 300D

At rest, the pressure for an R12 or R134A system will be between about 60 and 110 PSI, depending upon specified design charge level and ambient temperature at time of test.

Envirosafe is just propane, and I don't have data tables for that, but a system average pressure of 75 PSI sounds like there's "something" in there.

That pressure is high enough for the system pressure switches to operate and run the compressor. If the compressor is not running, you have a problem with a switch, the relay, the climate head, the fuse, etc.

Oh, when you try to run the system with the gauges connected (which if absolutely safe and fine to do), you should close both valves. That way you'll read the pressures correctly but no refrigerant can "cheat" and run through the valves instead of through the condenser.

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James Marriott
2003 Buick Regal
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