Bad 380C?

I’m having a hell of a time getting my system to build pressure, all lines have been checked and fittings are all leak free. I’m running a 165/200psi pressure switch with a Brand new Viair 380C compressor. I cant get it to build pressure in my 5 gallon tank past 145psi, it keeps running but refuses to build more pressure. After I shut it off it will drop down to about 120psi and stay there. I have added a Parker shut off valve to the outlet of the tank so I can rule out the rest of the system. I have also installed a new hose and inline check valve, but still have the same issue. I’m waiting on a SMC check valve to see if the viair units are both bad. I’m running out of ideas, anybody know whats going on here? Thanks, Mark.

There’s got to be a leak somewhere. Did you try using soapy water on everything?
BTW - Welcome.

Yup, I have tested every joint over and over and have no bubbles appearing anywhere. I even added the shut off to the outlet of the tank so I could narrow the problem down, but it refuses to build more pressure with it open or closed. My grounds are 10G wire direct to the frame and the power to the compressor is a clean 13.4-13.8V all the time. I’m going to put the SMC check valve in on Saturday, and if that doesn’t help, I guess I should talk to Viair about the actual compressor, it has less than an hour of use on it so far.

Welcome to the forum. I sent this link to Lance with Viair. If anyone can help you, he can!


If this is an older compressor, it may need a rebuild. Compressors that cannot achieve their maximum working pressure (or pressure switch “OFF” pressure) generally need a piston and cylinder replacement if no leaks are present.

If this is a compressor that is less than one year old, you may have a warranty claim. More information on warranty can be found at