Aux air control

When I turn aux air circuit breaker on pressure builds up to 55 lbs, then shuts
off and air starts gushing out right away with a lot of noise and sounds like its coming from inside the compressor. I have checked all connections and cannot see or feel a thing and the noise is 18 inches from me but I cannot see or feel inside of compressor.. IT leaks down to 50 lbs real quick then starts over and does same thing over and over and etc.If I turn circuit breaker off after it leaks down to 50 lbs it will hold that between 45 and 50 for several weeks.

Do compressors have relief valve when pressure gets over 50 or so lbs?

Do they have an adjustment to limit pressure to 45lbs or so?

Any ideas greatly appreciated! Dan & Jo

Dan, it is difficult to give specific information without knowing the compressor. In general yes air holding tanks have a pressure relief valve, often adjustable.
In general compressors have a cut in and a cutout pressure switch. Usually adjustable.
Each mfgr. has specifications of pressures that are not to be exceeded.

If you have adjusted the pressure switch at which the compressor cuts out (to have a higher pressure in the tank). You need to adjust the pressure relief valve to just slightly higher than that pressure. Do Not EXCEED The Mfgr's. Specifications!!

If you have not done anything to the compressor or relief valve you may have burnt (leaking) compressor valves.

You may have water contamination of the relief valve causing it to leak. Pop it off manually to clean it and re-seat itself.

Try to find the compressor manual and see what the Mfgr. says. Look on line it may be out there.

Dan...My first impression is the pressure switch for your compressor is set at 55PSI. I can understand that because your converter may have set your coach up so the aux. compressor only provides enough pressure for the regulated air system devices such as the floor slide or maybe the driver seat or generator air bags.

Generally a compressor has an over pressure relief valve, and also an unloader valve. The unloader valve will typically spit at the end of a cycle to dump head pressure so the compressor does not start under a load. That should result in a sound of escaping air at the end of the compressor cycle and then stop after a second or two.

The second valve typically found on a compressor (usually one with its own tank) is a pressure relief valve. The purpose of that valve is to provide some high limit safety. For example the compressor tank may be rated for 125 PSI, so the relief valve may start opening and dumping air at 115 PSI. Depending on the type, some reset themselves when the pressure is down safely some predetermined amount, and some require manual resetting.

Most larger compressors have a pressure switch that is adjustable.

As to your problem, my first reaction is your pressure relief valve or the unloader valve is making your compressor cycle. Because the compressor shuts off and then the air flow begins I would look to the unloader.

I would not rule out the pressure relief which may coincidently be set to the exact same pressure as the compressor cut out switch on the pressure regulator.

General thoughts....your aux air system sees full bus air pressure when the engine is running. Do you hear any air escape when the bus has just shut off? If not it may be that you have a check valve between full system pressure and the aux compressor pressure.

Also, some of us have aux compressors built into the bus by the converters that put out sufficient pressure to air up tires and level the coach.

I would suggest you contact Parliament and maybe Rick May in particular to get a better understanding of your coach's system.

My manual is in spainish and is only about warranty. Called manuf. and they said sounds like head gasket is busted. Jon and Jim, I will take it out this weekend as it is in a tight spot. It does have an ajustable knob off to the side where some hoses go in so I will try turning it little by little to check out youall's ideas. Thanks again for the help.