After much discussion about the air suspension, Richard found a detailed manual on the HWH website that discusses the operation of the air leveling and travel mode (thanks Richard). The system is somewhat more complex in travel mode than I outlined previously. There are not separate travel mode raise and lower solenoids as there are for the air leveling. There is a single travel mode solenoid for the right side of the axle and one for the left side of the axle. As Richard points out above, when in travel mode, BOTH these solenoids stay open all the time.
In travel mode, with the travel solenoid to each side of the axle open, the travel height valve(s) control the movement of air into and out of each airbag. There is an air supply going into each travel height valve (the valves are located in the center of the front at least on mid 1990 and earlier coaches, and one at the right drive axle and one at the left drive axle). When the travel height valve senses that the coach is low, the valve opens and sends air through the travel solenoid valve(s) and into the air bags. If the travel height valve senses the coach is high, it starts exhausting air thus allowing air to flow out of the air bags, through the travel solenoids and out the travel height valve exhaust.
As soon as you switch to level mode, the travel solenoids close, isolating the travel height valves from the air bags and allowing the raise and lower solenoids for each side of each axle to control the level height. If you or the automatic system, if applicable, determine one side is high, the lower solenoids for that side open which vents air out of the air bags to lower it. If it can't be lowered enough to bring the coach into level, the opposite side is then raised by opening the raise solenoids which allows supply air to be transferred into the air bags thus raising that side.
There were a several interesting statements in the manual.
1) Running the engine while leveling will provide a better air supply for vehicle leveling.
2) Never dump air before leveling, always level starting at travel height.
3) Always begin leveling side to side, making sure the the coach is level side to side before beginning the front to rear leveling.
4) Always drop the high side first, the raise the low side if required.
5) If it is necessary to raise the low side to get the coach level side to side, then use the RAISE buttons when leveling the vehicle front to rear. Trying to lower the ends of the vehicle when one side is completely lowered may twist the frame.
I have noticed that in automatic level mode on my coach, recommendation 5 is not always followed by the system. Even if a side is dropped completely, the HWH system stills tries to lower the high end before raising the low end.
I will repeat for those who have the Newell toggle switch for each corner of the coach rather than the HWH keypad, the two switches for each side or each end of the coach should be operated together. That minimizes twisting affects on the coach from the air bags.
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