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Could the AC compressor be the problem?

888 views 7 replies 5 participants last post by  RUResto 
#1 ·
I have been chasing leaks in the Vintage Air AC system in my 55. I recently changed to a cross flow radiator and installed a new Vintage Air Condenser for the cross flow. I initially had a couple of pinched "O" rings but think they are all fine now. No sign of leak with electronic leak tester. Yesterday I pulled vacuum for 30 minutes and then took off the vacuum pump and it held the vacuum for 1 hour and 15 minutes with no gage movement. I then charged the system and had 175 psi high side and 25 psi on low side with outside temperature of 82 degrees. The vent was blowing 41 degree air. The compressor was reading around 118-120 degrees when running. I thought all was fine, today the unit is blowing mildly cool air and the system shows around 60 psi on both sides without starting up the engine. I am now wondering if the compressor could be leaking when it is warm. Is this possible? Any suggestions would be appreciated. This one really has me stumped....
 
#3 ·
System off pressure means nothing more than there is some Freon in the system, high side / low side pressures the same when the system is not running = normal.

If all fittings & compressor seal do not leak: Turn the AC blower fan on low & sniff the vents to determine if the evaporator has a leak.

Compressor seal will show oil residue around it if leaking.

All sniffers are not created equal mine will detect a 1/4 lb a year leak.
 
#4 ·
Thanks for the comments. I realize the system equalizes when the compressor/AC is shut off. I checked running pressures tonight, about 26 hours, after the system was charged and got 75 psi on high side and 0 or slightly negative pressure on low side. It seems to keep low pressure for days, but won't keep an adequate charge for 24 hours. I am headed to Goodguys in the morning and plan on talking to Vintage Air. With the system loosing almost all pressure in such a short period of time I don't understand how it could hold a vacuum for over an hour? I may give in and use the dye to check it, I have been avoiding it so far. Didn't want to get it in my gages etc...
 
#5 ·
vaccum produces 28-30 in of vaccum

but look at the pressures you have when running,
so vac may not reveal the leaks.
I use my leak tester, engine off, so no air disruption,
also look for any oil,anywhere!
wipe off any you find and run it, look again.
check the bolts on the compressor, DO NOT OVER TIGHTEN!
same with the o rings. also the crimps, see if they twist,
also check the pressure switches, etc,
 
#6 ·
A leaking compressor shaft seal will do exactly as you have stated,after sitting thru the night you can find the leak with a leak detector at the compressor clutch. Leave the car inside a closed garage with the hood open as not to disturb any air around the engine while opening the hood. Freon is heavier than air so it will always be at the bottom of the compressor..
 
#8 ·
Well I am embarrassed at what I found. Drove it to Goodguys yesterday in Columbus. Had good discussion with Vintage Air, they felt it was a leak not the compressor. They mentioned a seal or "O" ring that would seal in one direction and then under pressure leak. This got me thinking, all my checking has been with the gages hooked up to the system. When the gages are removed, the Schrader valves open to the air. While I had used the sniffer around them in the past, I took a fresh look at them and got a wrench that could tighten them. Bingo, found the low pressure side could be tightened about a quarter of a turn. System after all the driving only took about 4-6 ounces of gas to get back to good pressures and 41 degrees vent temp. Drove it to cruise-in tonight and had plenty of cool air! The final test will be over time. Thanks to all for their suggestions and comments. I also agree that a better sniffer is now on the tool addition list!!
 
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