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Air Conditioner Continued Problem

A continuing problem with my A/C. I recently purchased a 1994 Olds Ciera S Wagon in mint condition with 87,000 miles from a retired couple. The owner stated he had trouble with the AC cooling and had a factory rebuilt compressor installed. The AC worked a short time and stopped cooling. Took it to my mechanic of many years, a very reliable experienced guy, and he checked it and found that when the compressor was installed the wrong fitting seals were used and he replaced them. It cooled for about 3 or 4 days of use and then quit. He recharged, put dye in the lines and checked all the fittings. The same results occurred. He checked and found no dye evidence of a leak. To make a long story short, we have replaced the evaporator core, compressor with a rebuilt Carquest unit, which comes with the dryer, orvice (sp?) and filter. Got the same results and never any evidence of dye leaking. Finally he put in a new ?stop leak? product for AC?s and in the same number of days the same results. Fortunately he has not charged me for a lot of the labor, as he is one of those rare breeds that believe if he didn?t fix it you don?t owe him. He is at a complete loss and cannot find anyone in this small town area that can come up with a solution. I have about $900 in this AC now and still no cool air. HELP!!!

The dye works fine for those areas where it can be seen where a leak may occur. But if the leak is at the evaporator, you can’t see the dye. For an evaporator leak, a refrigerant sniffer is required.

Tester

I assume that he has checked the hi lo pressure switch and taken pressure readings on the system when it is running. If the head pressure vacillates or builds up too much or the low presure is too low, it will eventually shut down the compressor but allow it to start up again when the pressure decreases assuming it is the former.

Do you lose cold air entirely or just now and then? Does he need to keep adding freon?

If the latter, there is definitely a leak somewhere since the a/c is designed as a closed system.

Describe the actual operation in more detail and it might aid those on the forum to better diagnose the problem.

To begin with, when it stops working is that it and then you need to add freon? Or does it start working again after awhile?

It is definitely a leak. The cooling capacity slowly diminishes over time and the system has to be recharged.

chiefbuzzard

I agree with Tester. Although the evaporator coil was replaced, it could very well be in that area. Pehaps one of the fittings or a problem within the coil itself. That would be my first area of inspection since he has checked everything else that is easy to get to.

Hang on to that mechanic or send him my way.

Do you mean the evaporator in the heater box was replaced? Or the condensor which sits in front of the radiator was replaced?

Tester

Your mechanic has got to bite the bullet and get a freon sniffer. With this sort of refrigerant loss, the sniffer might be too sensitive with a full load of refrigerant so just pressurizing with gas may be all you need. If the sniffer detects inside a closed compartment use a fan to blow the accumulated gas away before zeroing in with the probe.

Believe in Tester, he speaks the truth.

Has the mechanic checked the service valve ports for leakage? (not that rare a thing)

In theory dye should be present at those areas but in practice may not be.
Dye is ok to a point but an electronic sniffer is the only way to go.

A backyard method for an evap. test (somewhat iffy but it can work) is to place a perfectly clean container underneath the evaporator drain hose, turn on the A/C, and allow it to run for a while.
When a layer of water has been condensed into the container hold it up to the light and note if a slight rainbow colored oil film can be seen on the water.
If so, then the evaporator is leaking or possibly the evaporator hose fittings. (this is assuming for the sake of argument that there is a misinterpretation of evaporator and condenser)

The evaporator. A labor cost to remember! Almost everything on the back of the engine has to be removed to get to the cover and then after the cover is removed it is a job getting the evaporator out because of lack of working space. Thanks to all for the suggestions. Car goes back in his shop on Friday along with the messages I have not already relayed to him. Will let you know the outcome.