A/C manifold/ vacuum pump issue

Intenseman

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I have a manifold gauge set and vacuum pump purchased from harbor freight. I've had this set for more than a few years now. I was checking for leaks by pulling a vacuum on the system. It was pulling down -40 (which I believe is against the post) and when I shut the vacuum pump off the garage pops right back up to it's resting point at -25. It doesn't slowly go back like I would think it would do with a even a major leak. I'm thinking this is a tool malfunction.

I'll be honest, I don't know that this hasn't been the case for this equipment for years. I'd never checked for leaks this way before. I just discovered this procedure while reviewing a YouTube video before I charged the system. So something may have been wrong with my gear for a while.

Any thoughts?

Thanks,
Michael
 

PNW VietVet

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Equipment problem. Best vacuum I ever saw on an a/c gauge, was correct by the way, is 31" and I was below seal level. The elevation where you are will effect that reading but will still be good if say at 25" based on altitude. I would not want a manifold set and depend on it if I knew it was faulty.
 

swathdiver

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You can test for leaks on the manifold itself, no need to hook it up to a vehicle first. Lots of folks double check it this way first before testing for a leak on their vehicle, especially if the manifold hasn't been used in a while.
 

randeez

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I have a manifold gauge set and vacuum pump purchased from harbor freight. I've had this set for more than a few years now. I was checking for leaks by pulling a vacuum on the system. It was pulling down -40 (which I believe is against the post) and when I shut the vacuum pump off the garage pops right back up to it's resting point at -25. It doesn't slowly go back like I would think it would do with a even a major leak. I'm thinking this is a tool malfunction.

I'll be honest, I don't know that this hasn't been the case for this equipment for years. I'd never checked for leaks this way before. I just discovered this procedure while reviewing a YouTube video before I charged the system. So something may have been wrong with my gear for a while.

Any thoughts?

Thanks,
Michael


are you closing the valves on the gauge set before turning off the vacuum pump?
 

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