[Keith Jordan]

Wow, after you left Miami, Mike @"Land Yacht" had the exact same issue.

First thing to understand is that ALL air to and from the airbags originates at the six pack. Each bag is tied into a common header in the six pack. The solenoid valves tie into that internal header. The HCV ties into the internal header when the travel mode is activated. Otherwise the HCV is isolated from the header and therefore the bags.

In level mode, the appropriate solenoid will either add air to the header, or let air out of the header.

In your case, and in Mike's and Tom's, the coach is in travel mode, therefore the travel solenoids are open and the HCV is trying keep the coach at ride height. Remember the HCV supply is not from the six pack, although the HCV output goes to the six pack internal header. Except, if the raise solenoid is stuck or leaking, air is being supplied to the header through the leaking solenoid. This raises the coach, and the HCV sees the coach is too high and trys to let air out to keep it level.

If the lower solenoid were leaking, then air would be exhausting out the back of the six pack, instead of at the HCV.

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Wow, after you left Miami, Mike @"Land Yacht" had the exact same issue.

First thing to understand is that ALL air to and from the airbags originates at the six pack. Each bag is tied into a common header in the six pack. The solenoid valves tie into that internal header. The HCV ties into the internal header when the travel mode is activated. Otherwise the HCV is isolated from the header and therefore the bags.

In level mode, the appropriate solenoid will either add air to the header, or let air out of the header.

In your case, and in Mike's and Tom's, the coach is in travel mode, therefore the travel solenoids are open and the HCV is trying keep the coach at ride height. Remember the HCV supply is not from the six pack, although the HCV output goes to the six pack internal header. Except, if the raise solenoid is stuck or leaking, air is being supplied to the header through the leaking solenoid. This raises the coach, and the HCV sees the coach is too high and trys to let air out to keep it level.

The reason it stops at 90 psi is that is the pressure it takes to keep the coach at ride height. When supply drops to 90, the air pressure on the raise solenoid side and the air pressure provided via the HCV reach equilibrium. The failed raise solenoid is no longer raising the coach, and the HCV is no longer trying to lower the coach. 

If the lower solenoid were leaking, then air would be exhausting out the back of the six pack, instead of at the HCV.

Thank you for making it so even I understand.I will be going thru the rest of them with the tom rebuild kits.