Tom,
The control box for the HWH computerized leveling system is located on the ceiling of the front run electrical compartment below the driver's window. It is an aluminum box with a removable cover. On page 22 of the HWH 600 trouble shooting guide you will find what color wire and fuse controls that left front air bag. If the 5 amp fuse is blown, the issue may be the solenoid. If not, it may be an open circuit. The connections to the solenoids are close to the 6-pack. You are looking for a red wire labeled. "1600". Fred