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Venting AC HELP!


Nov 18, 2007
Irvine, CA
1988 Volvo 760T. Did the swap to 134a.

The car keeps blowing the charge at the back of the compressor. This happened to me last summer.... so i change the AC orifice valve, Condenser, and Accumulator. When the car holds the charge it blows ice cold.... but as soon as it gets alittle warm out side (85+) the car vents the charge.

Could my compressor be bad?

I pull a vacuum and then i put in 2.0lbs of charge with the right amount of oil.

I would suggest first replacing the orings on the compressor connections. If that doesn't cure the problem it might be something wrong with the compressor. Be sure to use the R134a spec orings. Even if you replaced the orings it would be good to doublecheck them. Because it's easy to pinch them or damage them without noticing.
IIRC the 700 series up to ~90 used a D-K compressor with the overpressure fitting on the back of the compressor, not on the accumulator, like the 240 w/ GM Delco system, which most 700's had after '86. My '91 240 has the vent valve at the accumulator.

So the question is, Does the refridgerant vent through the back of the compressor through the fittings on the high pressure side? Or through the vent valve?

Other thread: Where is the orifice tube on your car, in the firewall, like most 740's or under the dash?
the orifice tube sticks into the evaporator... located near the firewall.

the o-rings have just been changed.

im 95 percent sure its blowing out the vent valve since when the car does hold pressure and the UV dye shows those connections to be good.
IIRC on cars with the R134 conversion the compressors don't have the fill port or vent valve on the back of them and they need to be swapped out from the old compressor or put a tee in at the accumulator on the high side to fill from above and test high pressure easilly from the accumulator.
You may have a bad overpressure vent valve, maybe not. Without testing the high pressure side (especially when it vents) is the only way to find out what's going on.
Sounds like an safety over pressure valve.

As above, a high side pressure gauge would tell all.

This does not mean the compressor is bad, it may be moisture as it does not compress as much, debris in the expansion valve or over filling and getting liquid in the compressor. The heating of the condensor will raise the head pressure. Other things as well.

Gauges tell all.