The AC was not putting out much cold air, and the gauges indicated a bad compressor. Higher than normal pressure on the low side and lower than normal on the high side.Took the system completely apart, flushed all the lines, the evaporator and the condenser All blown clear with compressed air several times a day for about a week. Did not see any evidence of any blockages. New filter/drier and expansion valve. Installed a used compressor that I've had on the shelf for a few years but never used. Evacuated the system down to -27 in/Hg, leak checked for a few hours. All looked good. Added oil and Freon, expecting nice cold air. No such luck, worse than before, absolutely no cold air. Low side shows 90 and high side 130. The pressures equalize almost instantly when the engine is switched off.

Bad compressor or bad expansion valve?

 

Two bad compressors or one bad expansion valve?
With our type of expansion valve, I don't know how to diagnose their function, but your pressures sound compatible with a stuck open expansion valve. Maybe someone has the key to answer the question.
Good luck,
Dave

 

Seeing as everything else is new save for the compressor I would bet that that is your problem.

Get a new or rebuilt (Denso rebuilds are better than new) compressor and install it.

Both run right around the $350 price point and are well worth it. Just drain out the oil it comes with, flush it with what your system uses and then put in the correct amount.

You should do this sooner rather than later because when it really fails it is a nightmare to fix as it will send metal throughout the circuit.

You will have to replace all the parts you just replaced and do all that flushing over again. Speaking from experience

Best of luck getting this sorted!

 

Decided to do some experimenting. The first picture below shows the high pressure end of the expansion valve. This is the old one that was showing signs of being clogged. The plug has a 5mm Allen head indent. The second picture shows the insides of the valve. It appears that the plug is used to set the proper tension on the spring to set the degree of restriction to refrigerant flow.

High pressure side of the expansion valve

Inside parts of the expansion valve

I decided to take a chance and see if adjusting the expansion valve in the car would make any difference to the pressure readings. Was pretty sure this would ruin the expansion valve as I would have no real means of setting the right amount of tension but, if the pressures changed we would be pretty sure the compressor is okay. At worst I'd need to change the expansion valve again when the new compressor gets installed.

Sad to say that adjusting the plug on the expansion valve made no difference. Will be ordering another compressor and expansion valve shortly.

 

Sorry the pictures are a bit big.

 

You may want to consider the installation of an aftermarket in-line filter, as a part of your repair. No matter how well you have flushed the Condenser and the Evaporator, it is virtually impossible to rid them 100% completely of the debris that has accumulated from the failure of a compressor. But, (due in part to Murphy's unassailable laws) the normal circulation of the refrigerant and the refrigerant oil will be sufficient to dislodge enough particles to generate a never ending and unpredictable source of headaches.

 

I went through a similar set of symptoms and diagnosis on my '89 car. The problem turned out to be vacuum and actuator problems related to leaks in the vacuum system. Heated air was mixing back, and screwing with the low side readings. before you dive deep into the refrigeration-side symptoms, be absolutely sure that your vacuum-side components are working perfectly. I chased my tail for a bit on this and came to the same initial conclusion you did. Faced with what looked like a compressor problem, I looked at vacuum on a transient thought. In my case, the diaphragm on the heater control valve had failed. But it could be any of the vacuum-operated doors, or the blend door servo-actuator, or the vacuum plumbing including the solenoids in the console. Certainly worth a look before spending $$$ and hours on compressor replacement.

 

I second that. I spent months playing around with vacuum testers and the like and the fix was a new mixer valve - all of £16!

 

A bucket, a gallon of AC system cleaner, and a sump pump..and hoses to adapt.

Can flush through at large volume for a few minutes each section you go through.

GB and I tried it out when we redid my system in March, it visibly got way more stuff out than a simple once through air flush of fluid.

 

I really like that idea.
Doing the normal one shot air assisted flush has never seemed to be all that effective, at least from my point of view.

I could see doing one at the end to flush out whatever loosened up contaminants have been circulated during the pumping flush, but not trusting in the strength of the solvent to clean the system with only one pass.