[fjguercio]

PVT-Public..... about your question... Poster did not say how old or what he is working on. They did a vaccum test followed by a dye test. Did not find any leaks. So they have been "screwing" with the high/low pres valves a few times. The system has been charged a couple of times. Does not appear to be leak.... appears to be leaky valves. The research said in older car or one that is having odd issues that evade the obvious.... replace the valves, evacuate, and fill by the proper weight of freon for that vehicle spec. Check the system pressure and temps with observation till you reach operational temps. Should be done.

 

[fjguercio]

I need to do this AC work on 17 yr old toyota.... this is from my research & believe to be correct

I agree the dye was a good step.
Replace the high pressure and low pressure valve.... the locations where you test & evacuate the freon
When old these will leak after being used.... slow leak and hard to find.

Replace these 2 valves and do you work again.... skip the dye test this time