OT late model AC help needed...

My '92 GMC A/C is blowing warm air so I bought a kit that had three bottles of freon and a hose with a gauge. I've already had this thing retrofitted with R134 and had two compressors replaced previously. The gauge said 45-65 pounds (which means OK???) I was checking on the low pressure side as per the instructions, the hose wouldn't fit the high pressure side anyhow? I thought maybe something was goofy so I thought I would add some freon anyhow. Added maybe half a can and now the gauge reads over pressured and still blows hot air. What could the problem be?? The compressor is kicking on and off and the belt is turning, need help I am a retard when it comes to A/C...thanks

 

did you pull a vacuum on the system?the kicking in and out means that the refrig level is low.-it could also be the binary switch[hi-lo pressure sw]

 

Dan...low pressure side is the BIG hose.....did ya have the engine running AND was the compressor turning?? if so--- I would tke some OUT !! R134 uses a LIGHTER charge than R12....I would take it down to 25 lbs .....(maybe even less depending on your system).)You need a reading on BOTH sides to be able to trouble shoot accuratly.If you have a sight glass DON'T make all the bubbles go away with the charge...it WILL be over-full.Stick a thermometer in the vent and watch as you lower the (LOW SIDE)pressure...

Jersey Skip

 

Was your pressure at system off? Or with compressor running? The low side should be about 20-25 when running (although it will cycle and go higher then go down when the compressor kicks in). You really should have real gages with the high pressure side hooked up as well.

If that pressure was at rest, then you are low charge, it should be about 75-100 psi at rest. When you turn the compressor on, it pulls down the low side and increases the high side, typically 25 low and 250 high.

Your truck could have a blocked orifice valve. Especially if you have had two compressors replaced, did the system get completely cleaned out and flushed?

If your compressor is cycling real fast on and off, that is because the pressure switch. You may have to jumper it (just unplug and connect the two leads with a piece of wire) so you can get the refrigerant in. Caution, this will cause your compressor to run constantly and not cycle, so you really need to monitor the high side pressure when doing this. Means get real gages to do the job.