Leon Speed

Background: when I bought the car in 2007 the AC was blowing cool air, not cold. As part of the deal, the dealer refilled the AC. Better, but not really cold. After I fixed the vacuum pods in the dash it was a little better, but still not icy cold, on hot summer days (with a grey car and black interior) not very pleasant.

When I took the car out of winter storage last year, the AC wouldn't blow even cool, where it did before I put it in storage. I can't hear the compressor clutch engaging and the fans don't come on when the AC button is pressed.

I've done the following tests:
- expansion valve: feels neutral, not cold
- low pressure switch: 12 VDC on one side
- fan switch: 0,5 VDC on one side
- anti-freeze switch: 12 VDC on one side

I didn't check the voltage to the compressor because the connector is tucked nicely away. So, is this enough to conclude low pressure and probably a leaking system?

One more curiosity: I checked the low and high-side fittings, and the low side seems to be a R-134a fitting, but the high-side fitting doesn't look the same. Is this still an R-12 fitting? If so, makes me wonder how the dealer refilled the system?

dprantl

To me, the low side looks like R12 and the high side looks like R134a with a 90 degree right-angle adapter (why put that there?). Take the caps off and take pics, it will be easy to tell then. The test I always like to do to see if there is some refrigerant left in the system is to disconnect the compressor clutch wire, then with the engine running and A/C on, connect the compressor side to 12V using the jump post and see if the air starts blowing cold. If it's not cold after ~30 seconds and the compressor is turning, you know that either there is no refrigerant or the compressor is completely shot.

Dan
'91 928GT S/C 475hp/460lb.ft

dr bob

It wouldn't surprise me if you have mixed refrigerants. From the R-134a connector on the high side, one might assume that R-134a has been in the car. But with no stickers or labels that it's been converted, the dealer may have removed the low-side adapter and added R-12.

So the "right" answer is that

a) You have a leak someplace, and that should be fixed.
b) Whatever gas or blend you had in there has partially or completely leaked out
c) Without knowledge of what gas and oil are in there, you'll need to flush the system to get the old oil out before you add anything.

At this point you can decide which gas makes the best sense for you.

WallyP

I agree with dr bob.

I would start by trying to find the leak, hoping that there is still enough pressure in the system to cause detectable leakage. If not, additional gas will have to be added to find the leak. Nitrogen can be used if the leak detector is acoustic. If it is a refrigerant detector, it is a guess as to which refrigerant must be added to pressurize the system - shops will not want to chance cross-contaminating their systems, so that will be a problem.

Leon Speed

Ok, the clutch engages but it is still not cold. That means the compressor is (probably) good (I think).

Here are the fittings without the caps. The low side is a quick fitting, the high side indeed an original screw-on fitting.




Right. Didn't think of that. I thought though that mixing R-12 and R-134a is a big no-no. Anyway, it means I will have to replace all o-rings and from what I've read automatically the receiver/dryer.

R-12 is not allowed here anymore, so I'll have no choice but to go with R-134a.

Next step is to visit a Bosch Service Center to test the pressure.

Leon Speed

Wally, good point! I was simply assuming that O-rings are only source for leaking. I'm not quite following your second point about the type of detector and cross-contaminating, but I assume the shop will tell me how they will find the leak.

tonka858

take it to any auto shop have them put in a pound of r134 and some dye.

go back in a week or so and they can go over the car with a black light and find the leak.

you need a set of gauges on it to see if its low or plugged

Rich9928p

In my '87 S4, the expansion valves up front and in the Aux evaporator were leaking. After replacing the expansion valves, it made sense to replace as many of the O-rings as possible. She's blowing cold now.

Bill Ball

You've got that backwards. The low side is the original R-12 Schrader valve. The high side is an R-134a quick fitting. Lord knows what's in your system or how they filled it. Any even half-way competent AC shop would not have done this.

Leon Speed

Ok, high side front, low side back, got it. I don't think it was an AC shop, otherwise it would have had a label I assume. Anyway, off to the AC shop this time.

nuc

Depending on the shop, they may use a halogenated gas detector trying to see what is in there. If it is a mix of something and not straight 12/134a they will probably not want to reclaim whatever is in there, as it will contaminate their reclamation tanks.

Hopefully for you, it will have all leaked out. Then you need to find out what oil is in there, so that you know what refrigerant to add (after the leak is repaired).

Good luck, and this may be a good time to invest in some A/C equipment, as this stuff, especially when the mechanics start to get confused, can add up very quickly.

There are many people that can walk you through what needs to be done to get your A/C up to snuff.


'84 Euro 5 spd.

dprantl

It's never good when you have a mix of different refrigerant charge ports on the car. What most likely happened is the car developed a refrigerant leak and all the R12 escaped. The car was "repaired" by putting an R134a adapter on the high side, then charging liquid R134a in there. The best kind of R134a conversion. That of course also leaked out over time.

I would flush the lines, condenser and evaporator(s), remove the compressor and shake all the oil you can out of it, replace all o-rings, expansion valve(s) and drier, put in the correct amount of ester oil, evacutate the system with a proper vacuum pump, then charge by weight the right amount of R134a. Oh, and put on an R134a adapter on the low side. I would also remove the 90 degree fitting from the high side, there is no reason for it there. It may be useful on the low side, but I am not a fan of adding another potential leakage point. After all this, I hope the compressor has not been damaged by whatever mixture of refrigerants and oils the system was running. Good luck.

Dan
'91 928GT S/C 475hp/460lb.ft