A/C Refrigerent Line Pressure Switch

[billr]

Sorry, I can't guess where it came from. I zoomed in until the penny was about 8" diameter on my screen, saw lots of new detail on Abe, but the scraping was still fuzzy. It looks like a scraping from two tight-fitting parts sliding against one another, not a chip from a fabrication process. Best I can offer...

[fdryer]

Machining operations creates shavings from threading processes. With soft aluminum, threading processes creates metal shavings. Mass production with either manual or semi robotic automation still requires removing shavings. Sometimes shavings are inadvertently left in place as the process of inserting and screwing in valve cores proceeds. This may be what you found wrapped around the valve core. The bigger question is whether or not the fitting threads are damaged. There's also the possibility of the soft aluminum valve seat the flat O-ring seals against may be damaged, not allowing a seal.

[Luthin]

Thank you to everyone that contributed throughout this process. After analyzing the situation following Bill and Fdryer’s comments, I realized that I really didn’t have much to lose by simply charging the system again and seeing what happened. If there really is metal floating around in the system, the damage has already been done, and another tear down and replacement of parts would be required.
So I replaced the valve core that had metal shavings wrapped around it with a new one, and charged the system over the weekend. Outside air temperature was 90F with considerable humidity, and I was getting 48F vent temps going down the road. So I consider this to be a success thus far. The new valve core was not audibly leaking pressure even under a full charge, but if by the end of summer the system is no longer working as well as it is now (as being objectively measured via output vent temps going down the road) I will replace the discharge line with a new one. I figure that also gives me time to run the system and see if the new compressor hates me and really is self destructing and spewing metal all over the system.
Final pressures at 2k rpm were 32 low side by 250 high side with 90F ambient temperature.

As promised, below are my findings regarding the hoses that did and did not work for my replacement compressor. The replacement compressor and associated fittings were identical to the original compressor, although as another user noted in a different thread, the Four Seasons compressor’s discharge outlet is cocked at a slightly different angle, which routes the discharge hose over the top of the radiator. I got around this by gently bending the aluminum part of the discharge hose inwards towards the engine until it cleared the radiator in order to prevent any future maintenance issues down the road.

All parts purchased from Rock Auto unless otherwise noted.

Replacement compressor: Four Seasons Part #158529. New compressor, not reman.

The following hoses are confirmed to NOT work with this compressor:
Discharge Side:
GPD Part #4811719

Suction Side:
GPD Part #4811721
UAC Part #HA10350C

The following hoses are confirmed TO work with this compressor:

Discharge Side:
UAC HA111653C
GM Genuine 21031230
I firmly believe that Four Seasons 55792 would work as well, but did not have that specific hose to try.

Suction Side:
The only available hose that I could find and confirm to fit was from O’Reilly Auto Parts. It was a Murray brand hose with Part #55794. I find it coincidental that it shares the exact same part number with the Four Seasons suction hose, also 55794. The O’Reilly counterman said that Murray is a totally different company from Four Seasons and not just rebranding their hoses, but I don’t put much weight on that.

I did have a conversation with a very competent support rep at Four Seasons that assured me that their hoses #55794 and #55792 would mate up to their compressor #158529 without any modifications required. You can scroll through the earlier posts in this thread to find pictures of what my compressor mating surfaces look like, and if yours are the same, assume that you will have the same issues with the hoses as listed above. The hoses that will not work have a lip on the mating flange that prevents a flush connection with the compressor.

If I had it to do over again, and knew then what I know now, I would have just purchased the Four Seasons hoses from Rock Auto when I purchased the compressor. Alas, the GPD and UAC hoses were like half the cost of the Four Seasons ones, so I went the cheap route….

[fdryer]

One last tip if not done already - use a new set of service valve caps with either a built in rubber washer or O-ring and screw them on snug. This way you'll have two seals, the service valve and the cap for double sealing.

[Luthin]

Coincidentally, the new service valves came with new caps as well that had good solid o-rings in them compared to the caps that came with the hoses themselves. Those caps didn't seem to have much in the way of sealing at all.

My leak was on the high side though - would those little plastic caps and o-rings really do much to hold in 250psi?

Originally Posted by fdryer

One last tip if not done already - use a new set of service valve caps with either a built in rubber washer or O-ring and screw them on snug. This way you'll have two seals, the service valve and the cap for double sealing.

[billr]

No, they won't do much to seal the high-side. "Better than nothing", of course, but I made some brass caps for mine.

Be wary, too, that the male thread on the plastic cap doesn't protrude in far enough to slightly depress the valve stem. This can happen if you tighten the cap down as hard as you dare, and the male part starts stretching...

[fdryer]

Originally Posted by Luthin

Coincidentally, the new service valves came with new caps as well that had good solid o-rings in them compared to the caps that came with the hoses themselves. Those caps didn't seem to have much in the way of sealing at all.

My leak was on the high side though - would those little plastic caps and o-rings really do much to hold in 250psi?

With limited knowledge of mechanical engineering, there are two seals on each service fitting - the schrader valve and cap. The small surface area of valve core seal and seat, service valve cap using plastic threaded into the fitting and O-ring. My guess is the cap doubles sealing better than relying on service valves. Vehicles in everyday driving (rough handling of ac systems using aluminum tubing, high pressure hoses and fittings) are prone to eventual damage from wear and tear compared to refrigerators using copper and standing in place. Service valves offer convenient repairs on every vehicle. Refrigerators don't have service valves as a source for leaks with established reliability lasting at least 10-15 years if not longer. Central hvac systems have service valves. Brass fittings brazed onto copper tubing. The king valves have brass caps with O-rings and tightened/loosened with a wrench. Operating pressures are higher too.

A quote from Saturn service manual for '03 L200/L300;

IMPORTANT: Make sure there is an O-ring seal inside of caps before installation because cap is primary seal for A/C service fittings. Failure to tighten cap will result in refrigerant leakage.

[Luthin]

A few days ago the compressor(?) started making a low howling noise that correlates with RPM and seems to come and go. It's noticeable inside the car, but I don't really hear it when I pop the hood and put my ear near the compressor. It is DEFINITELY the result of the AC compressor in some form; turn the AC off and the noise goes away. The AC itself is still working beautifully. It kind of sounds like it's in the passenger footwell, but I dont think it's the result of refrigerant flowing through the evaporator. It's not really a 'flowing' kind of sound. I'd take an audio clip of it and post that but I doubt it would be audible or useful over the sound of the engine.

I don't mind a little noise if that's just what these cheapo Chinese compressors do. Or is this a sign of something else that went wrong? I still cant get those metal shavings around the valve stem from my mind...

[fdryer]

You have a choice of listening devices; a long handled screwdriver with tip pressed onto a part suspected of generating noise and the butt handled end pressed to one ear, a mechanics stethoscope or a long thick walled cardboard tube pressed to the suspected noise source with the other end pressed to one ear. Old school listening devices. Press either butt handle or tube firmly to ear, preferably against bone to transmit noise better. Try finding the source of the noise as soon as possible, especially if its the compressor. Oil should be circulating throughout the system and return to provide continuous compressor lubrication. Lack of oil returning to the compressor may cause the vanes to scrape chamber walls and create noise.

With ac running, put your hand on every aluminum tubing and feel for extremely hot or very cold temperatures. Discharge pressures should be warm to hot thru condenser coils, cooled to ambient temps leaving coils and entering filter/drier, wet suction line may be cool between evaporator outlet to rear of compressor.