Question on vac and charge of my AC system

[Michael L.]

Guys,

Sorry for the non-corvette question, but hoping someone can help me out. When I vac my AC system on my 70 GTO it gets to -30 on the vac gauges and I've read that it should hold that vacuum for some time after the pump is turned off. My system holds vac for about a minute then it slowly starts to fade. Do you think this is sufficient or is there likely a leak? The system worked and didn't leak prior to my removing the system for engine work a couple of years ago. During re-assembly I replaced all the O-rings. Thanks for any help you can give.

Mike

[Don H.]

Re: Question on vac and charge of my AC system

I am not an expert but I would say you definitely have a leak. It should hold for hours and may SLOWLY go down. Good luck.

[Harry S.]

Re: Question on vac and charge of my AC system

Guys,

Sorry for the non-corvette question, but hoping someone can help me out. When I vac my AC system on my 70 GTO it gets to -30 on the vac gauges and I've read that it should hold that vacuum for some time after the pump is turned off. My system holds vac for about a minute then it slowly starts to fade. Do you think this is sufficient or is there likely a leak? The system worked and didn't leak prior to my removing the system for engine work a couple of years ago. During re-assembly I replaced all the O-rings. Thanks for any help you can give.

Mike

Agree with Don, Did you dip the new green O-rings in R12 A/C oil? I'm assuming it's an R12 system.

[Michael L.]

Re: Question on vac and charge of my AC system

Yes I dipped the o-rings in A/C oil and it is an R12 system. The You tube video I watched on this said it should hold for 5-10 minutes so wasn't sure if I was at least close enough. I guess it's possible that the hoses and gauges are where the leak is and maybe the system would be OK but I'll probably have to put some freon in it and hunt for a leak.

[Michael L.]

Re: Question on vac and charge of my AC system

Oops. think I figured it out. I did not close the high side manifold valve when I first tried this. After closing both manifold valves it now is holding vacuum for the last 10 minutes.

[Justin S.]

Re: Question on vac and charge of my AC system

Michael,
If you close your manifold valves on your gauges then you won't be reading system vacuum or pressure.

[Michael L.]

Re: Question on vac and charge of my AC system

I was under the impression that the manifold valve opens the line in question to the center (yellow) hose but that the gauge is always connected to the respective hose. Is that not the case?

[Justin S.]

Re: Question on vac and charge of my AC system

My mistake. Yes you can close the valves to read static pressure but need them open to charge or pump down.

[Michael L.]

Re: Question on vac and charge of my AC system

OK thanks.