We had an air conditioning reading of 115 low side and 115 high side with the engine running and the compressor on. We replaced the expansion valve and receiver/dryer first. We evacuated the system for 30 minutes and it held vacuum at around 22 psi for 15 minutes. We put freon back in and the readings stayed at 115 low side and 115 high side with the engine running and compressor on. We then replaced the compressor and again evacuated the system for 30 minutes and it held vacuum at around 22 psi for 15 minutes.

We now have readings of 115 low side and 170 high side. Our low side just won't get any lower. With the engine off, the pressures equalize at around 90 on both gauges, so I am assuming that it is not my gauge that is sticking. It does not cool as we are not filling up the system with freon because the low side is so high.

Do we have a bad expansion valve or what else could be the problem? Or should I just put more freon in until the bubbles go away in the sight glass?

Thanks,
Greg