If your getting that kind of low side reading then the compressor should be fine. When they mess up from the valve it doesn't usually get very low on the low side.

Best way I have found to diagnose the valve is to go on a loooong drive with the a/c on. If it starts cooling eventually and works great when it finally does go to cooling its a bad compressor for sure.

If it never goes to cooling no matter what time wise then its not very likely to be the variable compressor. Also adding Freon will not effect cooling at all. If you add Freon and it cools its not the valve.

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