Residual Air Check

Turning the ignition switch from the Run to Off position clears all memory which is stored in the control module. Therefore, a test lamp (used during the actual diagnostic procedure) may not immediately indicate a failure when the ignition switch is returned to the Run position.
When charging the battery (battery is discharged when conducting the actual diagnostic procedure), the ignition switch must first be in the Off position or serious damage to the air compressor relay or motor may occur. However, use of a battery charger while performing the diagnostic tests (described further on in this section) is acceptable. Set the battery charger to a rate to maintain, but not damage, the vehicle battery. The following diagnostic test procedures are guides that will lead to the most probable causes of automatic leveling system problems. It is important to accurately identify the problem or condition before selecting and using the appropriate diagnosis procedures and charts described further on. Whenever conducting diagnosis procedures, always cycle the ignition ON then Off, before starting the actual diagnosis or test procedure to ensure vent solenoid and compressor reset ON times.

The air dryer has a valve arrangement that maintains approximately 8-24 psi in the air shocks to improve the vehicle's ride characteristics under light load conditions. To test this condition, proceed as follows:
1. Disconnect air line from the dryer assembly and attach it to one side of pressure gauge 0-2070 (0-300 psi), or equivalent.
2. Attach a short piece of bulk nylon tubing from the dryer to the other side of the pressure gauge. A compressor ball sleeve nut and sleeve for 3/16 inch tubing with ball sleeve connector and an internal pipe T fitting can be used to attach the tubing to the pressure gauge.
3. Cycle ignition switch from Off to ON position.
4. Apply a load of approximately 300-350 lbs. to operate compressor and raise the vehicle.
5. Remove load applied in step 4. Allow the system to exhaust and lower the vehicle.
6. When no more air can be exhausted, the gauge should indicate 8-24 psi.
7. Remove pressure gauge. Attach the system air line to the dryer and repeat steps 3, 4 and 5 to ensure system air pressure is within the shocks.