[Richard]

In the original scheme of things of that era, Newell’s were generally equipped with three compressors. The obvious engine driven one, a 120V one, and a 12VDC one.

Newell set up cascading pressures 12VDC 50 to 70, 120VAC 70 to 90, and engine 90 to 125. Kind of clever logic to keep the compressors from competing with one another.

A couple of things to keep in mind are that it really takes about 115 to 120 psi to raise the rear air bags. That is a factor of the weight of the coach and the air bag diameter. So, yes you are spot on, 90 psi will not level the coach. The HWH system comes with a bypass electrical switch. It is about the same size as the well pump switch, and it is usually close by the well pump switch for the 120V compressor. When the HWH system calls for leveling such as when pushing an up button, or if left in Autolevel mode, the system wakes up and tries to level the coach, the HWH control box sends a signal to the bypass relay and turns on the 120V pump BYPASSING the pressure switch. If you disassemble all that you will see it’s done with parallel electrical wiring.

I had a problem with that system, in that early in my ownership, I left it in Auto mode and the pressure went so high as to explode an airbag. It is supposed to have a high pressure relief in the system, but mine did not function as intended. Bottom line, I am not a fan of this feature, and have since disabled it. But it works great for leveling the coach if you are not in a hurry.

Sorry for all that context. You can certainly up the pressures on the well pump switch to enable the 120V to raise the coach. The only downside will be slightly shortened life of the compressor and slightly higher leak rates. You will notice that raising the coach on the 120V is agonizingly slow.