Help w/ AC Diagnosis

Make sure your high side gauge is accurate. Add R-134a. Sounds like you will need 2-3 cans of it. With system off, both sides should equalize about 85-100 psi. Running the low should be around

You're low on refridgerant. The low side should never be in vacuum. Low side should be about 30 psi and high side around 250 when the compressor is on. The needle should be steady, not wiggling. If it's wiggling, your compressor is in need of replacement. I would suggest that you fix the leak in your A/C system or the R134a that you put in will just leak out again.

-Bruce

You should have a decal under the hood with the proper charge weight. The charge weight is for an empty evacuated system and, does not matter if you are supplementing a system - you must rely on a good set of guages based on the temperature/pressure charts found in many service manuals. You may be able to find what you need at the local public library. Although I have never needed to go looking for it, I would assume this info is also available somewhere here on the net. Try a google search.

With the system off, both sides should quickly read exactly the same pressure and that pressure is only dependent on the ambient temperature of the system and the type of refrigerant inside the system. For R12, the pressure should be just about the F temperature, and for R134A, it should read about 10 psi higher. If this is not true, your gauges or hookup is faulty so fix that first. Since your static pressures don't make sense, you shouldn't trust the operating pressures to diagnose a problem. At