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Auxiliary Air Compressor Run-On.
03-29-2019, 22:19 (This post was last modified: 03-30-2019 14:49 by cmillsap.)
Post: #1
Auxiliary Air Compressor Run-On.
Here’s a bit of advice for all you Marathon owners. I learned to do this the hard way. Always turn off your auxiliary air compressor when leaving your coach for a long period of time.

I was two hundred miles away from my coach which is parked in Phoenix when my next space neighbor called me and said there was a loud whooshing sound coming from the front of the bus. This was happening about every 5 to 10 minutes.

I surmised that the auxiliary air compressor was not shutting off when the pressure cut-off switch hit 120psi. This allowed the air compressor to keep on running and building air pressure in the air tank to 180 psi at which time the tank relief valve would blow-off the tank pressure and the process would start all over again.

Being 200 miles away, I called my friend Steve Bennett, owner of Arizona Luxury Coach in Phoenix and told him my situation and asked if he knew a RV mechanic that could go to the coach and shut down the air compressor. Since we could find anyone available, Steve, being the nice guy that he is, volunteered to go shut the air compressor off for me.

While he was there, Steve decided to work on the problem and with some work and a call to Marathon, pinpointed the problem. There is a control circuit relay controlled by the air pressure switch located in the first driver’s side bay. This relay is in a box behind the ceiling mounted chair storage rack which had to be removed to gain access to the box and relay. The 120V contacts were sticking closed. This allowed the air compressor to run constantly. Manually unsticking the relay contacts and filing them made for a temporary repair and now allows the Air compressor to shut of when the pressure switch hits 120psi.

A new relay has been ordered and will be installed when received. A big “THANK YOU” to Steve Bennett for helping me fix this problem.

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