Decelerator or Hand Throttle (STD cab) Position potentiometer voltage is too high
Mid range clutch is not calibrated
Aux 3rd Lower Coil solenoid shorted to 12 volts.
Low pressure switch (+) input shorted to ground
Foot Throttle Position potentiometer voltage is too high (engine controller pin B30)
Mid range clutch is not calibrated
If Inadequate air flow is problematic, so clogged air filters, evaporator core air flow restricted, faulty blower fan motors, defective blower switch or faulty wiring or loose connections.