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AC Repair and Freon Leak

Please Help! I recently paid $1000.00 for AC repair on 2002 GMC Surburban. Now a week later it is blowing warm. When I called they said it might be a freon leak that they could not detect, because most freon leaks are not easy to detect with equipment. It seems this should of been found in initial repair and I am being told that is not the case. They are telling me this is another problem all together. This sounds wrong to me! Again, please help! PJO

My initial response is that they should have left you with a fully functioning, nonleaking system, however before I make that statement…what was the original bill for?

They certainly should have added a leak-trace dye to the refrigerant when they recharged the system. Did they?

That excuse is bogus. Any good AC repair shop should be able to locate a refrigerant leak using a refrigerant sniffer. These are sensitive instruments that can detect a refrigerant leak as small as a 1/2 ounce per year. If the refrigerant was lost within a week of the repair that’s a pretty large leak. And the sniffer should have started screaming as soon as it was turned on.

Tester

I agree with the use of a sniffer. Even the slightest hint of refrigerant will set mine to wailing.

Without knowing the details as to how the shop did the repair or any leak checking I would only add that the way I do things is pull a vacuum on the system, shut the gauges off, and then allow it to sit for quite a while. If it holds vacuum then there are no leaks; if it loses vacuum then it’s time to dwell on finding the leak, or leaks. This method prevents refrigerant waste and yo-yoing back and forth.

The only leak that might be hard to detect with a sniffer is one in the evaporator, which is buried in the dash in most cars. But usually a leak as bad as yours can be easily found with dye if it’s in the evaporator–the dye will run out the evaporator drain with the condensate, indicating a leak there. If the shop can’t find a leak as large as yours, they probably don’t know what they’re doing.

An evaporator leak is the easiest to find with a sniffer. Add a slight amount of refrigerant to the system, wait a minute or two, open the door and stick the sniffer in the passenger compartment. Because this area is confined the refrigerant concentrates in the passenger compartment and the sniffer starts screaming.

Tester

@Tester: Makes total sense. I’m just speaking from an experience I had with a truck I owned that was leaking. The sniffer couldn’t find anything but a slight leak around the compressor. When dye started coloring the water dripping under the truck, it was a good sign the evaporator was the culprit.

One place the dye might not be so helpful is at the port where you injected it. Naturally there will be some dye at the valve since that’s where the dye went in and if the valve itself is leaking, it might be overlooked. A sniffer would work better there.

Have a buddy who does A/C repair professionally and he does it exactly as OK4450 described. Pull vacuum and let sit. Why would you charge a system before you verified it was tight? Answer: it costs time and money while bay and equipment is tied up. Pretty sure with the old R12 systems this vacuum check step is mandatory to insure none escapes…

Thank you everyone for your responses! They charged me for a replaced compressor, receiver drier and charging the a/c system, a complete charge

Looking again, I do not see a mention of a leak trace dye.

Yeah if you are leaking down in a week its a major leak, as others have said it should be simple to find… It can be ANYTHING though from a bad O-ring on the compressor they replaced, to a bad evaporator they did not touch. The real question now is was your 1st compressor really bad, or did they just thow a new on in and hope for the best??

It’s possible that another leak could have cropped up over the past week that is not related to what they did but that brings up the point about how does the shop know this over the phone?

It’s the shop’s responsbility to make double sure there are no leaks when they return the car to after the original repair.
About all I can suggest is have another shop (preferably A/C specialists) leak check the car and then hit the original repair shop up about the results; especially if the leak is related to any service valve fittings, drier or compressor hose connections, or possibly even the compressor itself if it was a rebuilt unit.

It would be interesting to ask this shop how they check for leaks based on their comment about leaks not being easy to find.

Than they should stand behind their work. The system should have been fully leak tested and returned to you leak-free.

Well this only gets stranger…as I was heading to car shop I put the a/c on and it worked! I am now going to hold on and see if there is a pattern with it stopping to work as they day gets warmer or the car warms up. This has been intermittent this last week and something is wrong, but not sure what!

The leak might have developed due to the system being operated after the repair. But then it is possible that the shop overlooked the leak. I replaced the compressor on my pickup last summer and left a 30" vacuum for several hours with no loss before charging and a week later lost cooling and found the liquid line was leaking fast enough that it was quite oily. I certainly had no reason to rush or cut corners and with many years experience and all the needed tools at hand my “expert repair” failed in a short time. I feel certain that the shop wanted a happy customer. Return and let them look into the situation or take it to another shop for diagnosis of the leak. Sometimes “Crap happens.” Sometimes unavoidably, sometimes not.

I’ve attached a sketch of an AC system. If yours should stop working again, you could check to see that the line from the expansion valve to the compressor is not hot, the line from the various lines are at their apppropriate temperatyres. EDark blue is cold, green is cool to ambient, red is hot, and orange is ambient to slightly warm. Feeling the lines is not usually a definitive way of finding out exactly what’s bad, but you might find something that could help.

The way the system works is that the refridgerant is compressed by the compressor (and gets hot), the heat is removed by the condensor, then the cooled and compressed refridgerant is expanded wherein it becomes chilled and sent through the evaporator to absorb the cabin heat, and the now-warmed refridgerant is sent back to the compressor to do it over again.