hi guys I have found to have the same issue on my 1984 CLASS system, checked and resoldered the board, checked resistance of solenoid 30 ohm they call for all were 28.8 ohms. checked complete system for leaks. Turn on ACC fill up front, fill up rear to max turn to off then back to ACC and it releases the air......crazy.... put thumb over solenoid air outlet and can fill air pass on key ACC change.
any ideas