Automotive Air Conditioning Information Forum

Yes, I'm looking for opinions, and understand that there may be ones that differ widely. My intent is to review them without argument, then make the decision I feel is best for me.

This is a '94 SL2 for which my wife would like me to resurrect the A/C. The system is intact, no known (or suspected) damage or gross failures. However, the pressure is now down to zero (took with gauge recently) and has probably been there for several years. It did come with R134a. I checked with a UV light and see dye mainly at the big tube nut on the line entering the driver-side end of the compressor. There is also some specks of dye behind the compressor clutch, and on the condenser fins (top driver-side). I have not checked the drier, evap, or firewall areas with the UV; only areas easy-to-see from the front of the car. I do have gauges, an A/C vac pump, and a precision scale to weigh oil. One last bit of info: as I recall, the A/C stopped working when it still had good pressure, making me fear this is an X-valve issue.

So, what do you think it will take to bring this back to reliable long-term operation? Should I plan on replacing the compressor, drier, all hoses and X-valve? How about the evaporator and condenser? I could vacuum-check those when parts are removed, or even do a vacuum-check now to see how bad the over-all system presently is. Is it worth doing that?

If I just take it to a shop in the NorCal area, any guesses what I should ask for or expect to pay?

If I tear into this, can I keep the car operational while working on it? I can fab a belt idler to sub for the compressor while it is out

Although it runs well, it is a '94 with original clutch, engine, wheel bearings, struts, etc, etc. It is basically a $1000 car.

So, what do you think?

If it still had pressure when it quit, it may have been something as simple as an excessive clutch gap.

Any chance you can get an electronic leak detector? If so charge a few ounces & go looking for a leak.

The suction line nut on the compressor could be loose, I have seen it before. Try it with a wrench. I don't recall a nut type suction on the early Saturn - they had peanut fittings. Is this dealer installed A/C? Post a pic if you can.

Clean everything A/C under the hood throughly. Use some Gunk, follow up with a good surfactant like Simple Green or an orange cleaner. See if you can clean up the existing dye. You will want things clean to work on them anyway, and removing the old dye can save you time on future leaks.

Those block type TXV's they used are pretty reliable, and only about 60 bucks to replace.

It is a completely stock-OEM system. Also, I am almost certain it has never had any stop-leak in it.

It has been a number of years (5+) since it became inop, but as I recall my first steps back then were to check high/low pressures, add refig as needed, and confirm the compressor was turning (had to be, if high came up OK?). With pressures OK, I kind of suspected something deeper, like the valve block, so gave up on it. I don't feel A/C is a "necessity" in our area but... my wife does!

I'm assuming there has been moisture in there for a while now, even though the system is still "sealed", what with atmospheric pressure/temp/humidity changes and partial-pressure behavior of gases. All that good stuff.

"Stopped working" is a pretty general term, but I read it as the compressor stopped. If it was running, and not cooling it could be several things. Too bad you don't recall the exact pressures.

You have an empty system. The two choices are add refrigerant & diagnose the issue, or break it down & start over. Belt feeding a pile of parts in to a 94 Saturn is probably going to be costly. Finding the problem & fixing it will be a more cost effective solution than a TSR

First I would try evacuating it & see if it holds vacuum. If it has no gross leaks I would charge it & evaluate it. A new dryer should be installed, but since I can recover the testing charge I would wait until I knew more about the system.

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Yeah, that's what I'm leaning toward. Pull a vacuum, check for leaks some more, then charge back up so I can "update" the symptoms; get specific high/low pressures to post.

An update/bump:

No sign of leak (UV inspection for dye) at the X block on firewall or at drier behind LF fender.

I pulled a vacuum, it dropped from 29+" Hg to 27.5" in 36 hours. This was on a typical small mechanical gauge, not too accurate, but certain showed the trend.

Next, I pressurized to about 270 psi with argon. That dropped more dramatically; down to about 80 psi after only 24 hours. The drop in the first 15 minutes was not noticeable, though. Is argon a smaller, "more leaky" molecule???

I'm thinking i should clean the dye near the compressor clutch and low-side port, then charge the system so I can check for "new" leaks and see if the system is more-or-less functional if I can keep a charge in it.

Thoughts?

OK, I have some readings now. Bottom line is that there are a couple of obvious leaks at the compressor in/out ports, not the shaft seal; and it doesn't cool all that good. I would like to explore the "not cooling" before attacking the port leaks. If the poor cooling is because of the X valve, I would rather not have to fill this beast with R134a twice.

Low pressure = 30 psi at 2000 rpm engine speed
High pressure = 340 psi at 2000
Static pressure = 100 psi (engine off, high and low the same pressure)
ambient temp near high/low ports = 101F
ambient up near gauges = 88F
ambient in cabin =70F
cool air in cabin vents = 53F blower on full and set for recirc.
ambient humidity = 35%

Even when new, this A/C never was too eager, I doubt it ever got down below 40F, maybe not even close to it. However, that 53F seems kind of poor to me.

I can bleed off refrig to bring the high down, but that lowers the low, of course. I'm suspicious of the X valve, because of the poor cooling, but that is a pure guess! The leaks I can fix easily, but am clueless about what else I should do.

The low side is good, the TXV is doing it's job. The compressor is in good shape if t will push 340 psi

The 340 psi is a condensing problem. Either external airflow or internal refrigerant flow. It has a Parallel flow condenser, so either is possible.

First thing to check is the fan operation. Worn out fan motor, electrical issues, etc. I don't recall if the fan changes speeds on that car or not, hopefully you have a service manual.

A condenser AND a fan assembly would be under $250, using Delco parts.

You can mist some water at the condenser while it is running & see how far the high side drops. The low side should stay close to the TXV setpoint.

I "misted" the condenser a lot with 70% isopropyl alcohol, it didn't change the low/high a bit. Still 30/340 psi at 2000 rpm. Ambient is now 83F at 25% RH. I did a crude test of temps on the compressor inlet/outlet, just held a small TC against the lines. In = 63F, out = 145F

Does the receiver dryer have a cold spot on it?

340 psi is way too high for a discharge temp of 145f.