Bendix Commercial Vehicle Systems AD-SP SYSTEM PURGE AIR DRYER 10/04 - Manual (Page 15)

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B. If the AD-SP ™ air dryer is replacing an integral purge air
dryer such as the Bendix ® AD-4 ™ or AD-9 ™ air dryer, on
a vehicle equipped with a Cummins-Holset type E or
QE compressor, in addition to removing the existing air
dryer and correctly connecting the existing air lines to
the AD-SP
™ air dryer, it will be necessary to remove and
discard the Holset ECON and special orifice check valve.
See Figure 8.
PURGE CONTROL LINE
1. Install a purge control air line having a minimum inside
diameter of 3/16 inches between the AD-SP ™ air dryer
control port and an unused unloader port on the governor.
The control line must be plumbed direct to the governor
and not in series with automatic drain valves, lubrication
systems, etc.
2. The control line should slope downward to the AD-SP ™
air dryer without forming potential water traps.
DISCHARGE LINE
General:
Refer to Appendix A, Table A for recommended discharge
line lengths and sizes for various vehicle applications and
vocations.
PURGE EXHAUST LINE
1. If it is necessary to direct AD-SP ™ air dryer discharge
contaminates away from vehicle components a 1” (25.4
mm) I.D. hose can be clamped on the AD-SP
™ air dryer
exhaust
WIRING THE HEATER/THERMOSTAT
1. Determine the vehicle's electrical system voltage and
make certain that the AD-SP ™ air dryer that is to be
installed contains the same voltage heater. Confirm the
proper voltage by noting the color of the heater and
thermostat connector.
Heater & Thermostat Connector
Voltage Color
12 Volts ............................. White, (No other markings)
24 Volts ............................. Gray, or White w/Red Dot
The AD-SP ™ air dryer is available with either a 12 or 24 volt
heater and each uses 90 watts of power.
2. A separate wire harness and splice kit is with all
AD-SP ™ air dryer replacements and retro-fit kits. Refer
to the instructions contained in that kit for the proper
wiring procedure.
TESTING THE AD-SP ™ AIR DRYER
GENERAL OPERATIONAL STATEMENT
The AD-SP ™ system purge air dryer, operates differently
than integral purge air dryers such as the AD-9 ™ air dryer.
The "System Purge", designation is used because this air
dryer uses a small portion of the supply and front axle
(secondary) reservoir air pressure to purge or dry the
desiccant material. During the Purge cycle, an
approximately 8 - 14 psi drop in air pressure will be noted
on the front axle (secondary) service reservoir dash gauge.
The drop in pressure is the result of using a small amount
of air from the reservoir to purge the AD-SP
™ air dryer
desiccant.
The SC-PR ™ valve protects the air pressure in the front axle
(secondary) service reservoir, in the event of a compressor,
supply or rear axle reservoir failure or malfunction of the
AD-SP
™ air dryer purge control valving.
TESTING
Before placing the vehicle in service, perform the following
tests:
1. Close all reservoir drain cocks.
2. Build up system pressure to governor cut-out while
observing that both the front axle (secondary) and rear
axle service reservoir dash gauges rise equally in
pressure from 0 psi to governor cut-out. Note: When
building up brake system pressure to governor cutout
during testing, the engine/compressor should be run at
approximately 1,800 rpm to simulate normal operation
of the vehicle.
If either gauge fails to display this condition, stop testing
and check the installation of the SC-PR
™ valve. Note
that the AD-SP ™ air dryer purges with an audible escape
of air when governor cut-out pressure is reached.
3. Note that the front axle (secondary) service reservoir
pressure drops approximately 8 - 14 psi and that the
rear axle service reservoir loses no air pressure.
4. "Fan" the service brakes 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 at the
AD-SP
™ air dryer exhaust.
5. Test the operation of the SC-PR ™ valve. Build system air
pressure to governor cut-out and turn the ignition off.
Drain the supply reservoir and note that pressure in the
front axle (secondary) service reservoir does not drop
below 90 psi.
6. It is recommended that the following items be tested for
leakage to assure that the AD-SP ™ air dryer will not
cycle excessively:
(A) Total air system leakage (See Bendix publication
BW-5057 "Air Brake Handbook").
(B) Compressor unloader mechanism.
(C) Governor.
(D) Drain cock and safety valve in first (supply)
reservoir.
(E) All air connections leading to and from the first
(supply) reservoir.