BENDIX AD-IS User's Manual | Page 6

BENDIX Dryer User's Manual - AD-IS.
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6

A. Electric Power to the Dryer

With the ignition or engine kill switch in the RUN
position, check for voltage to the heater and
thermostat assembly using a voltmeter or testlight.
Unplug the electrical connector at the air dryer and
reservoir system 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 thermostat and
heater assembly to below 40 degrees Fahrenheit.  Using
an ohmmeter, check the resistance between the
electrical pins in the air dryer and reservoir system
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 thermostat and heater assembly to
approximately 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 heater and
thermostat assembly.

6. Pressure Protection Valves.  Observe the pressure

gauges of the vehicle as system pressure builds from
zero.  The primary or secondary gauge should rise until
it reaches approximately 106 p.s.i. (±6 p.s.i.), then level
off (or a momentary slight fall) as the next pressure
protection valve opens supplying its reservoir.  When
that pressure gauge passes through approximately 106
p.s.i. (±6 p.s.i.)  there should be an associated leveling
off (or momentary slight fall) of pressure as the third and
fourth pressure protection valves open. Then the primary
and secondary gauges should increase together until
they reach their full pressure of approximately 130 psi
(±5 psi).

If the AD-IS® air dryer and reservoir system does not
perform within the pressure ranges as described above,
recheck using gauges known to be accurate.  If the
readings remain outside of the ranges outlined above,
replace the  AD-IS® air dryer and reservoir system. NOTE:
There are no kits available for the servicing of the
pressure protection valves.  WARNING: Do not attempt
to adjust or service the pressure protection valves -
incorrect pressure protection valve settings can
result in automatic application of the vehicle spring
brakes without prior warning in the event one of
the supply circuits experiences rapid pressure loss.

REBUILDING THE AD-IS® AIR DRYER AND
RESERVOIR SYSTEM

GENERAL SAFETY GUIDELINES

WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO 

AVOID

PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following
general precautions should be observed at all times.

1.

Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
Always wear safety glasses.

2.

Stop the engine and remove ignition key when
working under or around the vehicle.  When
working in the engine compartment, the engine
should be shut off and the ignition key should be
removed. Where circumstances require that the
engine be in operation, EXTREME CAUTION should
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.

FIGURE 5 - PRESSURE PROTECTION VALVE LOCATIONS

PRESSURE

PROTECTION

VALVE

LOCATIONS

AD-IS®

AIR DRYER

GOVERNORS

ARE NON-

ADJUSTABLE

AND FEATURE A

BREATHER VALVE

IN THIS PORT

WARNING:

DO NOT ATTEMPT TO ADJUST OR

SERVICE THE PRESSURE PROTECTION

VALVES.  INCORRECT PRESSURE

PROTECTION VALVE SETTINGS CAN

RESULT IN AUTOMATIC APPLICATION OF

VEHICLE SPRING BRAKES WITHOUT

PRIOR WARNING.

 

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