Relief valve blows at 100 lbs

I have a Speedaire 80 gal 7.5 Compressor. The releif valve on the head blows at 100 lbs while compressor is running trying to make pressure. Is this a switch problem or is there a leak in the head causing pressure to develope too early. I have replaced the relief valve but that did not remedy the problem.I'm not sure what to do next....switch or replace gaskets

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Bill says...

Maybe you could take a second and read the page on PRV's, if you haven't done so?

http://www.about-air-compressors.com/PRV.html

If the PRV is letting go, it's normally nothing to do with the pressure switch.

Maybe also read the page on pressure switches if you haven't?

http://www.about-air-compressors.com/pressure-switch.html

I don't know what the normal PRV blow off pressure is of your Speedaire. It should be normally quite a bit higher than 100 PSI, as the normal high pressure cut out will be higher than 100 PSI.

The PRV is reading the system pressure, so if it's blowing off at 100 PSI and it's not supposed to, then as far as I'm concerned, you've got a PRV issue.

You can test your PRV if you have some simple air fittings and a pressure gauge. If it's blowing off at 100 PSI and it's not on your compressor, that reinforces that there is something wrong with it.

Good luck.

Bill