General

1.Visually check for physical damage, such as chafed or broken air and electrical lines, and broken or missing parts.

2.Check the Bendix® AD-9si™air dryer and mounting bolts for tightness. See Figure 1. Re-torque the three air dryer bolts to 720–912 in-lbs.

3.Perform the Operation & Leakage Tests listed in this publication.

1.This air dryer is intended to remove moisture and other contaminants normally found in the air brake system. Do not inject alcohol, anti-freeze, or other de-icing substances into — or upstream of — the air dryer. Alcohol is removed by the dryer, but reduces the effectiveness of the device to dry air. Use of these or other substances can damage the air dryer and may void the warranty.

2.For the Bendix AD-9si air dryer, there are no serviceable components or maintenance requirements that require the removal of the clamp band.

OPERATION & LEAKAGE TESTS (REFER TO THE TROUBLESHOOTING CHART IN THIS MANUAL)

1.Check all lines and fittings leading to and from the air dryer for leakage and integrity. Repair any leaks found.

2.Build up system pressure to governor cut-out and note that the Bendix AD-9si air dryer purges with an audible escape of air. Watch the system pressure and note the pressure fall-off for a ten minute period. If pressure drop exceeds—a) for a single vehicle: 1 psi/minute from either service reservoir; or b) for tractor trailer: 3 psi/minute from either service reservoir—inspect the vehicle air systems for leak sources and repair them.

Refer to the Symptoms 1 and 4 in the Troubleshooting Chart.

3.CAUTION: Be sure to wear safety glasses in case of a purge blast. Check for excessive leakage around the purge valve with the compressor in the charge mode (compressing air). Apply a soap solution to the purge valve exhaust port and observe that leakage does not exceed a 1" bubble in one second. If any leakage exceeds the maximum specified, refer to Symptom 4 in the Troubleshooting Chart.

4.Build up system pressure to governor cut-out and note that the AD-9si air dryer purges with an audible burst of air, followed immediately by approximately 40 seconds of air flowing out of the purge valve. Apply and release the service brakes several times to reduce system air pressure to governor cut-in. Note that the system once again builds to full pressure and is followed by a purge. If the system does not follow this pattern, refer to Symptoms 5 and 6 in the Troubleshooting Chart.

5.Check the operation of the air dryer heater and thermostat assembly during cold weather operation as follows:

A.Electric Power to the Dryer (Refer to Figure 4)

With the ignition or engine kill switch in the RUN 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 connections of the female connector on the vehicle power lead. 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

Note: These tests are not possible except in cold weather operation.

Turn off the ignition switch and cool the Heater and Thermostat assembly to below 40° Fahrenheit. Using an ohmmeter, check the resistance between the electrical pins in the air dryer connector half. The resistance should be 1.5 to 3.0 ohms for the 12 volt heater assembly, and 6.0 to 9.0 ohms for the 24 volt heater assembly.

Warm the Heater and Thermostat assembly to approximately 90° 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 heater and thermostat assembly.

When rebuilding or replacing components of the air dryer and reservoir, use only genuine Bendix® brand replacement parts. For ease in servicing, the AD-9si air dryer has been designed so that maintenance kits can be installed without removing the air dryer from the vehicle. CAUTION:

Always depressurize the air dryer and purge volume by slowly removing the plug in port 22—and drain all other reservoirs on the vehicle—to 0 psi before servicing the air dryer.

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 shown in this manual or the Bendix® Quick Reference Catalog for the appropriate kit(s). The Quick Reference Catalog (BW1114) can be ordered and viewed on line at www.bendix.com.

Note: Kits are not available for servicing components inside the air dryer purge volume.