[77newell]

Well goodness Richard was right again (not surprising really); a problem like this is never solved until proven over time. Upon arrival back home in Michigan the inability to raise the left rear with the leveling controls re-emerged. DRAT!

While it was still misbehaving I cross-connected the leads to the two rear "raise' solenoids and the problem stayed with the left rear so that proved it was not an electrical signal problem. I then undid that and cross-connected the tubes coming out of the 6-pack and attempted to raise the rear, the left rear didn't come up much so that proved the problem was downstream of the 6 pack. Well, I had already changed the tubing between the 6-pack and the ping tank for the left rear and the problem persisted so that wasn't the problem. All that remained were the ping tank, the hoses to the air bags and the air bags. Since I couldn't conjure up a way the ping tank or air bags could cause this on-again off-again behavior I chose to change the hoses. While sitting in the driveway the problem has not reoccurred, but as Richard so smartly says: "it isn't over until you've been down the road a bit".

Here is why I think the problem has been solved. A visual inspection of the hose from the ping tank to the tee that feeds the air bags showed a sliver of rubber showing at the end of the steel insert that goes into the hose as part of the end fitting assembly. The old hose was destroyed in the process of installing new hoses. I suspect the rubber inner liner of that hose had a small leak in it that allowed compressed air to pressurize the outside of the liner. That only became a problem when the pressure inside the liner dropped to the point the liner collapsed. Once collapsed the pressure in the ping tank had to be substantially reduced for quite awhile for the air outside the liner to leak away and the liner then returned to its proper position. This logic explains why the leveling raised properly following my replacement of the tubing from the 6-pack to the ping tank which took several hours with that side completely depressurized and then had the problem re-emerge later when the system had been pressurized for a long time.