HVAC Pressure Testing
05-15-2009, 05:31 PM
#1
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Thread Starter
HVAC Pressure Testing
About 20 years ago, when I bought my 928, the aircon worked great. A couple years later, a micro switch broke in the a/c head, which I wired in a new switch. And then over the years in storage, the aircon stopped working, I assume due to lost freon. I'd also expect the orings had dried. And finally, the compressor locked up. Pretty bad state.
So, I replaced the compressor, all the o-rings, rebuilt all the hoses (yes all), replaced the drier and the expansion valve and new oil.
What I want to do is two things:
1. test the electrics to see if the aircon clutch will kick in, and
2. test that the system hold pressure.
I know I need pressure to get the clutch to engage and I do not want to load a bunch of freon (R-12) in the system just to find a leak the stupid way.
Is there another gas I can buy to load up and test the pressure?
I assume if you jumper the pressure switch on the drier, that would be one way to test the electrics for the clutch's operation?
I don't think I want to recharge myself (but I might). But I know I don't want to drop her off at a shop without knowing what the state is.
Thanks
So, I replaced the compressor, all the o-rings, rebuilt all the hoses (yes all), replaced the drier and the expansion valve and new oil.
What I want to do is two things:
1. test the electrics to see if the aircon clutch will kick in, and
2. test that the system hold pressure.
I know I need pressure to get the clutch to engage and I do not want to load a bunch of freon (R-12) in the system just to find a leak the stupid way.
Is there another gas I can buy to load up and test the pressure?
I assume if you jumper the pressure switch on the drier, that would be one way to test the electrics for the clutch's operation?
I don't think I want to recharge myself (but I might). But I know I don't want to drop her off at a shop without knowing what the state is.
Thanks
05-15-2009, 05:38 PM
#2
Drifting
I'm assuming you refilled it with mineral oil that is only good with R-12?
Some will say that the way to test for leaks is to vacuum the system and see if it holds vacuum. That can be helpful in finding leaks, but leak detection isn't the primary purpose of vacuuming the system. You vacuum it to remove moisture.
Even with oil, you don't want to operate the system without refrigerant.
If everything is back together, the only thing to do at this point is have it vacuumed, recharged, and see what happens.
Some will say that the way to test for leaks is to vacuum the system and see if it holds vacuum. That can be helpful in finding leaks, but leak detection isn't the primary purpose of vacuuming the system. You vacuum it to remove moisture.
Even with oil, you don't want to operate the system without refrigerant.
If everything is back together, the only thing to do at this point is have it vacuumed, recharged, and see what happens.
05-15-2009, 06:06 PM
#4
Race Car
Use Nitrogen gas to test for leaks. Crank it up to 100psi and shut of the tank valve and leave it for a couple of hours. If it's still at the same level, you are good to go.
Dan
'91 928GT S/C
475hp/460lb.ft
Dan
'91 928GT S/C
475hp/460lb.ft
05-15-2009, 07:29 PM
#5
Electron Wrangler
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If you just want to test the compressors clutch operation - jumper the pressure switch and with the car not running - but ignition on - activate the AC and listen for the clutch engaging.
I think it would have been wiser to save the new drier for install at the time you are ready to immediately pull a vacuum...
Alan
I think it would have been wiser to save the new drier for install at the time you are ready to immediately pull a vacuum...
Alan
