A/C question

[notny41]

Hi all, I have an '86 951 that the air does not currently work on it. I believe it has a non-original and different-than-factory compressor on it. A couple years ago I charged the system with R134a and it lasted a few days. So I figured I had a leak in the system somewhere. I tried turning the a/c on when I drove it about a week ago and no cold air came out, which didn't surprise me in the least. But today I went out and removed the covers to the schrader valves on the low and high side and each of them had pressure in them...

What should I make of this?

[Tom]

Hi all, I have an '86 951 that the air does not currently work on it. I believe it has a non-original and different-than-factory compressor on it. A couple years ago I charged the system with R134a and it lasted a few days. So I figured I had a leak in the system somewhere. I tried turning the a/c on when I drove it about a week ago and no cold air came out, which didn't surprise me in the least. But today I went out and removed the covers to the schrader valves on the low and high side and each of them had pressure in them...

What should I make of this?

Not sure how much you can read into all that. The system shuts the compressor off if the refrigerant gets too low, and many an a/c system will only leak under pressure, but not all the way down to nothing. So, it's quite possible you are low on refrigerant due to a leak, but that the leak only happens over X psi. That exact scenario happened to me last month. Of course, you could have something else wrong entirely such as a bad compressor or expansion valve, etc. Can you see/tell if the compressor clutch is engaging? If it's engaging, then that would suggesting something other than low refrigerant. If it is not engaging, I'd probably start by having the refrigerant evacuated if there is a meaningful amount left, and then testing to see if the system will hold a vacuum. A vacuum test can confirm a leak, but it can't 100% confirm you are leak free. My condenser had a leak, but held vacuum just fine -- probably because it only leaked under higher pressures. Still, it's a good starting point.


If you are going to DIY it, Harbor Freight sells a/c gauges and an a/c vacuum pump.

[whalenlg]

FWIW - I’ve borrowed the same tools for free from O’Reilly in the past.
If the compressor is working, refilling refrigerant with dye or an electric ac gas sniffer can also come in handy if you need to track down leaks. At least one of my ac ports ended up as the culprit

[Tom]

FWIW - I’ve borrowed the same tools for free from O’Reilly in the past.
If the compressor is working, refilling refrigerant with dye or an electric ac gas sniffer can also come in handy if you need to track down leaks. At least one of my ac ports ended up as the culprit

Dye and a sniffer are both great suggestions! I found the general area of my leak with my Harbor Freight sniffer. After a lots of little beeps here and there, when I finally put the sniffer near the leak in the condenser, the sniffer went crazy and left no doubt about it. I then took the condenser out and pin-pointed the leak with compressed air and soapy water. Re the ports, the last time this happened, my ports were leaking too -- specifically the cheap R12 to R134a port adapters I bought on Amazon. I had to replace them with a better set.

[notny41]

Well, I got a sniffer and was waving it around under the hood and got to where the intercooler tube goes down to the front of the car and the sniffer started reacting. I pull it away and it settles down - move it back there and it starts beeping furiously again. It seemed like it was right in there at the condenser. Tom, how big of a job is it to get the condenser pulled out? I'd imagine the front plastic nose piece has to come off?

[Tom]

You might want to try some dye to confirm, just in case it's coming from the fittings or something, but it does sound like you have a leaky condenser.

Removing and replacing the condenser is surprisingly easy. The hardest part is removing the black lip under the front bumper. Other than that, the bumper cap itself stays on. The condenser is held in the car with two M6x20 bolts. You just remove those, and undo the two refrigerant fittings, and possibly a little rubber clamp that holds the refrigerant lines to the side of the condenser, and the condenser slides right out the bottom. The top of the condenser is locked in place by sliding over two rubber mounting nubs. I don't have the batwing on my bumper these days, and have the luxury of a lift, so with all that I could literally have the condenser out in 5 minutes or less....

condenser-removal.jpg (633.59 KiB) Viewed 462 times

[notny41]

Much thanks @Tom !

[notny41]

If I were to pull the condenser off and want to pressure test it, would a person want to cap off the two lines before driving the car - or should I not drive the car til the condenser is back on the vehicle?

[Tom]

As long as you change the receiver drier on re-assembly and pull a good vacuum, I'm not sure it matters all that much for a day or three. I put little silicon plugs in the fittings to keep oil from dripping out.

[dr bob]

If I were to pull the condenser off and want to pressure test it, would a person want to cap off the two lines before driving the car - or should I not drive the car til the condenser is back on the vehicle?

As long as you change the receiver drier on re-assembly and pull a good vacuum, I'm not sure it matters all that much for a day or three. I put little silicon plugs in the fittings to keep oil from dripping out.

I'm a fan of keeping the system closed as much as possible, especially if you are driving the car. Tom's plan with the silicone plugs is great. I think I have a collection of those originally purposed for powdercoating projects.

Especially when the car will be driven or otherwise at risk for those plugs falling out, a nitrile glove offers five different-sized prophylactic sleeves to slide over the exposed tubing or hose connectors. Secure those with cable ties, tape, or even rubber bands.

Similarly, I'd have the connections on the condenser itself protected as soon as they are open. With the tape wrapped around the finger sleeves, there's a certain amount of mechanical protection for the threads. Plus, unless the front area of the car is surgically clean already, it makes sense to keep stuff from getting into the condenser as you R&R it. Isopropyl alcohol is pretty good at removing the adhesive residue after common electrical tape in this instance, should that need arise.

If you do plan to drive the car with the condenser out, take a moment to unplug the compressor clutch coil wire and secure it safely. The systems have low-pressure protection and of course we'd never accidentally hit the AC button by accident on a warm-day drive. But, just in case, ...