cab air ride wont raise

[longlivesuperdogs]

2002 RD cab suspension wont raise from resting position, i know it normally wont raise until somewhere around 75-80 psi in system, but neither will the seat (seat may have air to it at lower pressure and just wont raise my by butt till its gets to this point IDK), but now the seat will raise, but not the cab even at 130psi, is there a valve, other than the leveling valve under rear of cab i should be looking at?

[slpwlker]

how fast are you dropping pressure? I had a problem on my Pete the airline under the cab cracked and had a pretty massive leak, both seats wouldn't work. Also check the cab bags. Leveling valve could just be shot at this stage.

[longlivesuperdogs]

no leaking air, thinking leveling valve myself

[smorse54]

HI, if neither the seat or cab will raise it's the little pressure protection valve. This valve limits air pressure going to seat and cab leveling valve. Don't know on an RD exactly where to tell you to find it, but it will be on an air tank.

[skip]

Just check the ride height valve under the back of the cab, it should only have 2 air lines going to it. One is the supply and the other is delivery to the air bags. If you are getting a good supply of air to the valve, then disconnect the height control rod on the valve and move the lever up and down manually and see if raises the cab or not. If this is the case then you have a crook valve. If you are not getting supply to the valve then, as mentioned earlier it will be a priority valve on the tank.

[EastTex Cartage]

I had the same issue and I was under the truck greasing and inspecting and found that the ride height valve had failed - that is the little white plastic tube had broken in two.