If the check valve is shot (and unloader is OK), it will continue to hiss (constantly) until the compressor kicks back on. This is common. The compressor will try to cycle frequently to restore the pressure. Everything will seem fine while the compressor is running. Once it reaches pressure and shuts off (actuating the unloader), it will hiss constantly again, etcetera.
Yup. I went out and played with my C/H today. If it shuts off on it's own (switch made) it hisses air. If I turn it off early from the disconnect it doesn't "unload" and it grunts when it restarts. (I didn't try that too many times). I vote for the unloader being bad too. Sorry about the check valve FUD. (Unless machine this predates unloaders).
Had the same thing happen to me, turned out it was a bad breaker in the circuit box. Swapped breakers and it's been running fine every since.
Jim Kohan snipped-for-privacy@neo.rr.com
I was also thinking start up load. Sometimes the electrical switch has an adjustment, so you can set the "turn on" pressure down a bit lower.
Or you can make a pinhole leak right after the compressor, so that when the comp starts, it's under zero pressure. Needs a check valve after the pinhole leak.
Best bet is to check the volts and amps at startup, and see if that tells you something useful.
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