EvansTempcon systems have inherent vacumm leaks. Always have. The Vacumm motors are not air tight. So, the 12 volt pump will cycle. NOTHING can be done to fix this.
The AIR bag system is Frtliner installed and the HWH system taps into the Air bag system. So, you can have a problem with Frtliner or HWH. Frtliner does NOT work on HWH systems. HWH jacks are installed by Newmar and the Harness and solenoids are HWH parts as is the wire harness to the solenoids. If the fuse blows, odds are you have a shorted solenoid, but a long shot would be a short in one of the 3 dump valve wires in the HWH harness. This is a link for your year model HWH service manual. You will have a 300 or 600 series HWH system IF NOT computerized(Auto) leveling, this is a good Service manual. Doug
https://www.hwhcorp.com/ml13514.pdf
