Bendix Commercial Vehicle Systems AD-9 IPC AIR DRYERS 4/11 - Manual (Page 7)

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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 fi ttings 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
GENERAL
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.