Thanks for checking the air conditioning on my car. You were friendly and prompt as usual. However, a strange thing happened. The next day, a neighbor with lots of self taught mechanical experience was explaining generally how the ac's work. We were looking at the ac in the car. He had mentioned to me about the possibility of the expansion valve possibly being stuck or blocked in some way. He traced the high and low pressure lines to find the area where the expansion valve was probably located. Then he asked me to start the car and turn the ac on full blast. I did so, and he pointed out the the high pressure line was hot to the touch and the low pressure line was cold. He said it looked like it was working fine. The air inside was cold. I told him, " Yeh, but just wait until it gets a little warm and it will quit cooling. We waited with the car running for 10 minutes or so, and it was still cooling. We took it for a test drive of about 10 or 15 miles, and it just kept on cooling. We have been driving the car since with no signs of a problem. I drove it to Georgetown and back today, and it is still working normally.
I know the car had not been cooling well at all prior to the time I brought it in to you. You surmised that the compressor was failing internally and producing only small partial spurts of cooling on an intermitant basis. My neighbor and I did nothing to the car except look at it , except that we did attach the little cheapie guage that I have here at the house just to see how the pressure would register. It was in the high normal range.
It is a mystery I cannot explain, but am happy that it is working again. Just hope it continues to do so.
Thank you for your input on this. I am glad your system is working at this time. No one wants to spend money, including myself. Please let me explain our reason for our recommendations.
Your ac system does not have an expansion valve. It has an orfice tube that is protected by a fine wire mess screen. Should this screen become clogged then the freon cannot flow, producing the same symptom as a restricted expansion valve. What can cause the restriction ? I will also explain this in detail. If the disaccant bag in the drier ruptures it will release particles into the system which cannot pass through the orfice which in turn will create a constant blockage. The same goes for particles being released from the compressor due to internal failure. These particles are generally much smaller in size compared to the disaccant material. They can however cause a blockage once enough particles have built up on the orfice screen.
The compressor used in your car is a Variable Displacement Compressor. These were designed to aid in less fuel consumption and run quieter. The V7 compressor in your car does not use a low pressure cutout switch. Instead it uses an Refrigerant Control Valve (RCV). These can and will fail which will produce the symptoms you are having. Some shops will replace just the valve and let it go that way. Sometimes this works and sometimes it does not. We have tried replacing these in the past and have had negative and positive results. I do not want any negative results so I have decided that we will not replace just the RCV because I do not want to inconvenience my customers by them having to come back for the same problem. When this happens, not only does the customer have to do with out the car but we have to return the money collected for trying to side step the correct fix which is compressor replacement. When the compressor is replaced the orifice tube, the drier are replaced along with a system flush to insure that the system in clean and free of any debris that may damage the new compressor.
I hope this helps explain our recommendations and also helps you make a decision if your system should start acting up again.