Automotive Air Conditioning Information Forum

I have a 1996 Cadillac Seville. The air wasn't blowing very hard, so I had the system drained and checked my orifice tube and it was filthy. I replaced it and the accumulator also. I pulled a vacuum and let it sit for about 45 minutes. Both gauges were pegged negative and didn't move, so it was not leaking. I had a friend put new refrigerant in and we stopped about an ounce short of what my manual said because it was blowing very cold and very hard and he didn't want to over charge it. I drove it about 6 miles home and it worked flawlessly. I live in Fl and this was at the end of the summer. I didn't use the AC again for several months as it's not a daily driver and the weather was very nice. When it warmed up, I switched it on and got a low refrigerant warning which shuts my compressor off. I checked the system and it was empty. If it held a vacuum and was fine when I drove it home, what could have happened for the refrigerant to leak out in the interim? Thanks for any help!

da324 wrote:what could have happened for the refrigerant to leak out in the interim?

You got it: a leak !!!

Yea, I was hoping for something a little more helpful as in why would it hold a vacuum and then leak after refrigerant was put in? As in what might be the cause in that scenario?

Cusser is right, of course. The system has a leak someplace. The hard part is finding it. With a car that old, it could be leaking from literally anyplace. And just because it held a vacuum or negative pressure doesn't mean that the system won't leak when charged under positive pressure.

I'd start by checking under the hood to see whether there are any oil stains on or near the A/C components, especially around the hard lines down low that might be subject to additional corrosion. Sometimes, a hidden pinhole can develop in an insulated hard line that's very difficult to find. In particular, I'd look for oily foam insulation on any of the hard lines that could indicate such a leak. I'd check all the rubber hoses as well for evidence of cracks and/or the presence of oil.

It could also be a bad o-ring at one or more connections, a leaking condenser or evaporator, or a faulty compressor shaft seal. I'd ensure that the caps are in place on both the LP and HP schrader valves because the caps themselves do the sealing, not necessarily the schraders.

If no leaks turn up after inspecting all of the above, you could try evacuating and recharging the system once again along with adding a little UV dye. Then drive it for a couple of weeks with the A/C on. Afterwards, check all around the A/C components for the presence of dye using the appropriate goggles and light. Any leaks should show up brightly. Don't forget to check for the presence of dye in the condensate, which would point to a leaking evaporator.

Alternatively, you could use a "sniffer" to check all around for leaks, although a sniffer might not work well, if at all, should the leak be extremely slow.

The gunked-up orifice tube is suspicious. Normally, the OT should be fairly clean unless the compressor disintegrated at some point in the past and the compressor was replaced without the rest of the system being serviced correctly, or some kind of sealer was introduced into the system.

Put a shower cap around the front of the compressor after verifying there I refrigerant in the system. Let it sit overnight and place a sniffer thru a small hole. se if the sniffer activates. If it doe, could be the shaft seal.

Thanks, I will try those things. The car is old, but it only has 100k original miles and is mint, I bought it with 50k from the original owner 18 years ago and have kept everything updated. Hopefully, I can use the info provided to get the AC working, If it's the evaporator, then, it will not be fixed as the motor has to be removed, or the body has to be raised off the motor to get to it because it's behind the dash. Thanks for the help!

To your knowledge, has the A/C system ever been serviced over and above what you guys did to it last year?

From what you said, the evaporator case must be in the engine compartment and not under the dash, where it would be more accessible but still not very easy to get to. If sealer was never introduced into the system and the evaporator isn't leaking, I'd just leave it alone and concentrate efforts elsewhere.

Here's hoping luck is on your side.

To my knowledge, the unit had never had any issues, or serviced before I bought it. However, it never really blew very hard. It was cold close to the vents, but here in Fl if it's not hitting you somewhere on your body, it doesn't feel super cold. Night time always felt colder for obvious reasons. When I replaced the orifice it was blowing harder, so I thought for sure that was it. However, I was just told that a dirty orifice is usually the result of a faulty compressor. I'm out of town at the moment dealing with a death in the family, but I will check it when I get back and post my findings. Thanks for the info!

My money is on the shaft seal-- look for oily/greasy slinging oil traces/debris anywhere near the front of compressor- like on radiator hose or frame...they were famous for this issue. And holding vacuum doesn't always mean it can hold refrigerant......