40400 central air compressor runs but no pressure buildup

by Jack Sacco
(Palm Harbor, Fl )

40400 central air compressor runs but no pressure buildup

40400 central air compressor runs but no pressure buildup

Problem: No pressure buildup. Tank and tool tap- off gages both read zero while compressor is running.


While the unit was on:

1.Oil level-OK.

2.checked copper pressure line from motor to the tank fill valve/ connection and tap off for the pressure switch-pressure- ok.

3. I pulled out the safety release valve at the pressure switch - pressure released.

4.No air leaks from `under tank` valve.

5. No other tank leaks detected.

6. Replaced damaged copper nut/ferule connector at tank inlet. Thought this would have resolved the problem since the nut was cracked. But no luck.

Pressure switch issue??

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Oct 22, 2018
40400 no pressure buildup?
by: Bill

Thanks for the detailed question. Info always helps.

No, it isn't a pressure switch issue, as the pressure switch essentially turns the compressor on and off and has nothing to do with pressure building.

Regarding this "2.checked copper pressure line from motor to the tank fill valve/ connection and tap off for the pressure switch-pressure- ok." I'm not sure what you mean by OK?

If you, with the compressor off, remove the line from the pump head to the tank, start the compressor, and use a gloved finger to cover the output, can you block the output air?

If you pull the intake filter, do you feel air huffing back out when the compressor is running?

Did you, with an empty tank and power off, remove the tank check valve to ensure it wasn't blocked?

The checks you did were good, but insufficient to nail down the problem.

Please see this page, and then scroll down to the links to pages about compressors that run and don't build pressure:

https://www.about-air-compressors.com/troubleshooting-your-compressor.html

I suspect a pump issue.

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