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high side service valve

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Sep 12, 2016, 1:08 PM

Post #1 of 5 (680 views)
high side service valve Sign In

1996 Chevy C3500 7.4L 269,000 miles

When I got this truck the AC didn't work. I've put a set of gauges on it and both registered a static pressure of 0 . Pulled vacuum to about -28 hg and that didn't hold either, slowly lost vacuum. System was empty. Pressurized system with compressed air up to 90 psi hoping to find a leak. It didn't happen until I disconnected the red hose from the high side. I could hear the air escaping from the high side service valve. I knew I'd need to replace it so I got out a Schrader valve remover. Since the valve is vertical I couldn't see the Schrader inside. Pushed down on the tool and began to try loosening the Schrader. Couldn't get it out!!! Climbed on the front bumper to see what was wrong and found that there was no schrader valve in this service valve. Not sure whether it is a ball with a spring or what. Compressor is not seized and the clutch will cycle on and off. Tested it with the vehicle turned on, AC on and an air pressure charge of about 80 psi for about 4 seconds.

Could you enlighten me on this and suggest whether I should replace it with an original type valve or with a Schrader type and why? Thanks for the reply.
EPA 608 & 609 Certified / kc8frw at gmail dot com / 8106894032 (call or text)

(This post was edited by johnbkobb on Sep 12, 2016, 1:16 PM)

kev2 profile image

Sep 12, 2016, 1:20 PM

Post #2 of 5 (674 views)
Re: high side service valve Sign In

A picture would help - On some the whole valve would unscrew from the line - look for a hex head fitting at bottom of valve at line/hose and just unscrew.

google dorman Part No. 800-955

(This post was edited by kev2 on Sep 12, 2016, 1:24 PM)

Ultimate Carjunky / Moderator
Discretesignals profile image

Sep 12, 2016, 1:39 PM

Post #3 of 5 (666 views)
Re: high side service valve Sign In

Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 12, 2016, 2:24 PM

Post #4 of 5 (656 views)
Re: high side service valve Sign In

Those ball seats do suck but you don't have an option to use anything else. DS showed you what needs to be changed.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 12, 2016, 9:48 PM

Post #5 of 5 (647 views)
Re: high side service valve Sign In

Ball valve - ditto - suk. They really do depend a lot on an OE cap for the final seal and should. Shouldn't leak while gauge set on it though or hear it leak if so a new one carefully like DS showed - carefully,


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