Hey I got a 2000 corvette that has never had AC since I bought it due to a bad compressor. I found a used compressor that was working when it came off a low mile car. I bought new lines and filled the compressor with oil and I installed it in the spring. I just now got to vacuuming and charging the system. I vacuumed the system and it held over night. My compressor would not come on because I had no refrigerant in the system so I jumped the compressor and it now comes on. I went to put the bottle in and it would not take any. I waited about 20 minutes and the LOW side pressure kept climbing until I shut it down at about 145 PSI. The HIGH side was lower at about 120 PSI. Any ideas in what this could be?

 

it could be the compressor, low mile, or not. How OLD is the compressor? Many things, like seals, etc., have a 'shelf life'. Could be the orifice 'screen'. Did you put a new one in?

 

It was from an 03 I believe. I replaced everything on the AC system with new stuff except the compressor. It also is for sure not leaking as it held vacuum perfectly over night.

 

Did you plug the AC pressure switch in?

 

HUH ???

You pull a vacuum on the system (typically using a vacuum pump hooked to the system thru a manifold gauge set) - and get down to a vacuum of more than 29" Hg. Then you shut the valves, disconnect the vacuum pump and hook up a pressurized tank of refrigerant - open the valves and no refrigerant flows into the system ??

That really doesn't make ANY sense !!!! I would start by checking the connection from the tank of refrigerant to the manifold gauge set. Even without the compressor runing - the system pressure should equal the tank pressure.

Then in the 2nd half of your post - you say that you're eventually able to get 145 psi on the low side, and 120 psi on the high side with the compressor running ???

Again - that makes little to no sense.

Shut the compressor off - within a few minutes - the system pressure will equalize, and high & low side pressures will be equal. Verify that's what the gauge set reads. If that is not the case - I think you're gauge set is bad. If it does equalize - note the pressure number - with near 90 ambient temps - static pressure should probably be around 50 psi. If so - start the compressor, and watch the gauge set. If the system is working correctly - the low side pressure should slowly drop to around 25 - 30 pis - while the high side pressure should rise.

 

Yeah it is

 

I think you nailed it on the gauges being bad. They are used rentals from az. Makes sense if the LP valve is stuck and just building on the gauge without going in the system.

 

I have another thought. Sometime in the last several years the R134a suppliers that fill the shelves at auto parts stores, and other retail outlets with the 12oz cans, have changed the cans to a different type of discharge port. It's now a sealed port that doesn't lose refrigerant when you unscrew the can from the fill hose, or gauges. I ran into this on some Harbor Freight gauges. The new style cans won't work with my gauge set, even with that 'special adapter tool', a blue colored, screw-on plastic piece. I can still pull a vacuum on my gauges, but now have to recharge using the store bought can and hose method, as the gauge set I bought will not fill the A/C system. Hope this helps.......