Unloader Valve hissing upon operation

Hi Bill,


I have a Champion vr3-8 vertical compressor. 3hp 80 gallon.

Anyway as soon as the compressor gets around 50psi it starts hissing out of the bottom of the governor housing directly under what I believe to be the unloader valve.

Its not a steady stream but more of a pulsing hiss.

Once you shut off the compressor the valve does the normal release and the compressor seems to be holding air as it should. I don't believe it to be a check valve issue.

I am assuming the unloader needs to be replaced however I just wanted an expert opinion before I start throwing parts at it. Thanks in advance.

Robert Lee

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Apr 26, 2017
Unloader leaking during compressor operation
by: Bill

Well Robert, if it is the unloader that's pulsing out air while the compressor is running, then I'd certainly be looking at the unloader as the problem, as it should be closed while the compressor pump fills the tank.

On the other hand, if the unloader is operated by a lever from the pressure switch, you might watch the lever while the compressor is running to see if it's moving up and down. If so, it may be a symptom of a spring problem in the pressure switch.

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