Air Brake compressor cycling on/off

['05 LLY Chev Kodiak]

2005 Duramax Diesel (LLY with only 46,000 miles)

Chevrolet Kodiak C5500 medium duty

35' Super C Gulfstream Enduramax Toyhauler RV

 

Just yesterday when I parked it and turned it off the (or what I am assuming is my) airbrake system started cycling on and off.

 

I was hearing the pump cycle on for 90 seconds every 3 minutes just like clock work (off for 3 minutes and then on for 90 seconds). I ended up disconnecting the battery to stop the cycling until I can get it resolved. I am now trying to get a mobile Technician to visit the RV site to diagnose it but am not having much luck in spite of calling the local large truck service centers (GM Medium Duty Dealer, Pilot J, Camping World, North Trail RV etc.).

 

I am wondering if anyone has any ideas on what the problem may be. On the surface I am wondering if there is a sensor that may have calved.

 

Thank You

Paul

P.S. VIN: 1GBE5U1275F504097

[Ledrbuk]

If you get power to the air pump with the key off it's the relay located under truck next to air pump. It is bad and is running the air pump till the pressure switch says the tank is full and shuts it off. Also have a small air leak or check valve leaking.