2003 Ford Taurus - Compressor not engaging

[JohnHere]

Besides the last statement, what did I do incorrectly here, and why is it venting with what should be the correct weight of charge?

The pressures are reasonable at idle, but I would re-check pressures at about 1,800-2,000 RPM to determine whether the high-pressure side is actually too high. Ordinarily, the pressures—if within normal range—shouldn't cause refrigerant to vent through the High Pressure Relief Valve (HPRV).

With further testing, the high-side pressure might prove to be too high, or the HPRV could be shot.

The HPRV is a one-time valve—that is, once it vents, it needs to be replaced. Unfortunately, the system will have to be recovered again to replace it.

The under-hood decal shows the same specification for R134a that I have: 34 ounces net weight.

[DSK]

Thanks John, I'll test it at 1800 RPM and check pressures again.
I'm not seeing separate HPRVs offered locally at part stores or online, including ACKits. I wonder where they can be had. I only see them attached to the manifold hose assembly.

[JohnHere]

You should be able to find the correct HPRV at your local Ford dealer. Bring the old one with you, if possible, along with the engine specs and compressor maker, so that they can match it for you. If memory serves, I believe 3 or 4 different V6 engines were offered for the 2003 Taurus. I'm unsure whether the HPRV differed for each engine.

It's also possible that the car has a combination of a bad HPCO (High Pressure Cut Off) switch that fails to shut-down the compressor under extreme pressure conditions, along with a condensing problem that's causing the high-side pressure to spike and the HPRV to vent. If so, you should be able to identify the abnormal high-side pressure when you re-test it and take the appropriate corrective action.

A word of caution: Be aware of unusually high pressures that result in venting refrigerant from the HPRV. Refrigerant that releases suddenly and unexpectedly is hazardous, especially to the eyes and exposed skin. To prevent this from happening, watch the high-side pressure carefully. If it starts to spike above normally expected levels, shut off the compressor right away until the cause is found and fixed.

[DSK]

Time to close this one out. Thanks for the assistance from everyone.

A quick recap for anyone possibly using this in the future.

Problem #1 was the compressor not engaging even after 12 oz of freon at static pressure. The solution was getting a good connection on the clutch cycling switch to the schrader valve beneath. I also could have tested continuity between the switch to see if there was a closed circuit/connection. Obviously that would have saved a lot of time just testing there first.

Problem #2 was system venting through the HPRV. This was with a full spec charge, venting at probably around 1800-2000 RPM. Unsure of pressures, as I was driving. But idle pressures just prior were 45/225. I had just installed the suction/high pressure line that comes off the compressor, containing the high pressure switch and the HPRV (the system had been recovered at the shop. I evacuated and vac tested, then recharged).

I ended up taking this in to a shop, bringing the original HPRV off the old line.

Solution: the shop belives the new HPRV that came with the line was faulty. They installed the original, and no more venting. He brought me out to the car, showing me what was happening as he revved it up to 2500 RPM. We watched the high side climb to 325 then at around 340, the cooling fans kicked on high speed which held the pressure from climbing further. He told me the HPRV should not have vented until the gauge was pegged out at 500 psi (true?).
Anyway, there's the solutions. I sure feel stupid, but I'm inclined to agree that there was something wrong with that new HPRV after what we found. I'll buy any other product brand before I buy a UAC product again.
But to be fair, if anyone can think of something I could possibly have done in my installation process to cause this problem, please share it.

Grateful for the forum and all the assistance.

[JohnHere]

The high-pressure safety switch normally shuts-down the compressor at around 406 PSI, so it's possible that the switch was defective (allowing the pressure to build to where the HPRV vented), the HPRV was defective, or both. I never tested a HPRV as to its release pressure, but 500 PSI sounds reasonable if not a bit high.

Glad you got it sorted out.