Pressure Test Pressure

[HVACRSA]

I recently purchased a used car and the air con has a leak somewhere on the system. I am in the process of doing a pressure test on it but was wondering what the recommended pressure is to use for the check. I currently have it at 150psi but not sure if I should increase it to help locate the leak.
Any suggestions would be appreciated!

[cadwaladr]

I recently purchased a used car and the air con has a leak somewhere on the system. I am in the process of doing a pressure test on it but was wondering what the recommended pressure is to use for the check. I currently have it at 150psi but not sure if I should increase it to help locate the leak.
Any suggestions would be appreciated!
200psi should do it,what make of car is it,once they get to 3/4 years old, condensor lets go.

[HVACRSA]

200psi should do it,what make of car is it,once they get to 3/4 years old, condensor lets go.

From what I can tell the condensor has been replaced and looks new. I just checked the pressure and it has dropped! Will jack it up to 200psi tomorrow and start the search! GRRRR!! And tips??? Never looked for a leak before on a car... I have a leak detector but will try the trusty old soapy water first.

[Brian_UK]

Bear in mind that it could be leaking from the compressor shaft seal.

These can dry out if the system has not been run, or been empty for a time.

Sometimes a pressure test can close up seals giving a indication of success. I used to test cars by increasing the pressure slowly in say 25psi stages.

[monkey spanners]

I wouldn't put more than 120psi in it if it were stood next to it.
I was taught to use 100psi as a general rule, and 120psi max in car air con systems.

If its not showing up with what you have in it and you have checked with soapy water or an electronic detector round connections and the condenser, i'd vac it out and recharge with some uv dye.

Jon

[HVACRSA]

Managed to find the leak. One of the pipes had chaved through on the bullbar mounting bracket! There was still some dye in the system from previous work that must have been done on it so actually turned out pretty easy to find the leak.
Thanks for all the tips.

[cmcct]

Hey there,
I see the problem has been solved, but I'd like to mention something about the shaft seal. Unless the shaft seal has had a major failure, boosting the system with nitrogen may actually mask the problem of a leaking shaft seal. I usually rely on my micron gauge to tell me if the shaft seal is leaking if that is what I suspect the problem is. I pull the system down to 1500 microns then spin the clutch plate and see if the micron gauge climbs to atmosphere.

[SWECAR]

A very good remark, often also if running the vaccumpump you will hear a change of noise from the pump, when turning the plate, if leaking of course.

[Boss302]

Yep, you better be careful with the amount of pressure you use in a car. I have seen a guy blow up an evaporator in a pickup before. Blew the hole heater box apart. They aren't made like a unit is. I wouldn't go over 150 psig.