General

4.Check the operation of the safety valve by pulling the exposed stem while the compressor is loaded (compressing air). There must be an exhaust of air while the stem is held and the valve should re-seat when the stem is released.

5.Check all lines and ﬁttings leading to and from the air dryer for leakage and integrity.

6.Check the operation of the end cover heater and thermostat assembly during cold weather operation as follows:

A.Electric Power to the Dryer

With the ignition or engine kill switch in the ON position, check for voltage to the heater and thermostat assembly using a voltmeter or test light. Unplug the electrical connector at the air dryer and place the test leads on each of the pins of the male connector. If there is no voltage, look for a blown fuse, broken wires, or corrosion in the vehicle wiring harness. Check to see if a good ground path exists.

B.Thermostat and Heater Operation

Turn off the ignition switch and cool the end cover assembly to below 40 degrees Fahrenheit. Using an ohmmeter, check the resistance between the electrical pins in the female connector. The resistance should be 1.5 to 3.0 ohms for the 12 volt heater assembly and 6.8 to 9.0 ohms for the 24 volt heater assembly.

Some early models of the Bendix® AD-9®air dryer will have resistance readings of 1.0 to 2.5 ohms for the 12 volt heater assembly and 4.8 to 7.2 ohms for the 24 volt heater assembly. If the resistance is higher than the maximum stated, replace the purge valve housing assembly, which includes the heater and thermostat assembly.

Warm the end cover assembly to over 90 degrees Fahrenheit and again check the resistance. The resistance should exceed 1000 ohms. If the resistance values obtained are within the stated limits, the thermostat and heater assembly is operating properly. If the resistance values obtained are outside the stated limits, replace the purge valve housing assembly, which includes the heater and thermostat assembly.

REBUILDING THE BENDIX® AD-9®AND AD-9®IPC AIR DRYERS

If, after completing the routine operation and leakage tests, it has been determined that one or more components of the air dryer requires replacement or maintenance, refer to the maintenance kit listing in this manual or the Bendix® Quick Reference Catalog (BW1114) for complete kit information.

When rebuilding or replacing components of the air dryer, use only genuine Bendix parts. For ease in servicing the Bendix® AD-9®and AD-9®IPC air dryer desiccant cartridge assemblies, it is recommended that the air dryer be removed from the vehicle.

The kit illustrations on the following pages show the kit contents and will be referenced throughout the rebuilding procedures.

BENDIX® AD-9®AND AD-9®IPC AIR DRYER REMOVAL

1.Park the vehicle on a level surface and prevent movement by means other than the brakes.

2.Drain all reservoirs to 0 psi (0 kPa). — Caution: compressor discharge line may still contain residual pressure.

3.Identify and disconnect the three air lines from the end cover and note the position of end cover ports relative to the vehicle. See Figure 1.

4.Unplug the vehicle wiring harness from the heater and thermostat assembly connector on the purge valve housing assembly. See Figure 6.

5.Loosen the 5/16" hex cap screw and sleeve nut securing the upper mounting strap to the upper mounting bracket. See Figure 7, illustration A.

Some air dryers may contain a one piece upper mounting strap as shown in Figure 7, illustration B. If this is type of strap is present, loosen the adjustment locknut and remove the strap and isolator from the upper bracket.

6.Mark and remove the two 3/8" end cover cap screws, locknuts, and four special washers that secure the lower mounting bracket to the end cover. Also be sure to mark these two holes of the end cover. (These bolts are longer than the other 6 bolts.) Retain the mounting hardware. See Figure 7, illustrations A and B.

7.Remove the air dryer from the vehicle.