Air Suspension has me Stumped

[Hawk in WY]

I am committed to restoring the eas on my 1994 LWB Classic. Spring advocates need not reply.

I have replaced the air bags and ride height sensors with new parts and the ecu with a used part allegedly from a truck with working air suspension.

I recently resealed the valve block.

The suspension came up to ride height immediately with the new valve block and worked fine around town.


After driving over 55 mph for around 5 minutes, the suspension slowly dropped to the bump stops or with minimal air in the system. This happened with an earlier valve block and i replace the delay sensor. Error message was "Exhaust value permanently closed." I cleared the error, but the suspension stayed on the bump stops on restarting. Would not respond to the up or down buttons.


I checked again and no errors were found. I cleared again and still on the bump stops. After a few minutes driving the suspension came up again, but then dropped again to the bump stops after driving over 55 mph.


Stopped, checked again, no error messages, cleared again. This time left side came up, right side still down.


No error messages. Drove with a list to starboard for maybe five minutes, below 55 mph, and it eventually leveled out.


I got the "Exhaust valve permanently closed" only once. Clearing the error did not allow the suspension to reflate.

Any suggestions of where to look for the remaining gremlin much appreciated.

Thanks in advance.

New information: On start up top and bottom lights illuminated. Believe that indicates a soft fault. New error message: "Pressure sensor not changing state. Always on." Never seen that one before.

Cleared the fault. Suspension comes back to normal but do notice light on the down button blinks for a very long time when suspension lowered which I believe indicates compressor still running which supports weak compressor.

All suggestions welcome.