BENDIX AD-1 Service Data - Page 15

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SYMPTOM

1. Dryer is constantly

"cycling" or purging.

2. Water in vehicle

reservoirs.

3. Safety valve on the

air dryer "popping off"

or exhausting air.

BENDIX

AD-2

AIR DRYER TROUBLESHOOTING

CAUSE

A. Excessive system leakage.

B. Excessive leakage in ﬁ ttings, hoses and

tubing connected to compressor, air

dryer and ﬁ rst reservoir.

C. Defective check valve between the air

dryer and ﬁ rst reservoir. (In standard

AD-2 air dryer, check valve to outlet port.)

D. Defective governor.

E. Leaking purge valve in the air dryer end

cover (control side).

F. Compressor unloader mechanism is

leaking excessively.

A. Desiccant requires replacement.

B. Improper discharge line length or

improper line material.

C. Air system charged from outside air

source (outside air not passing through

the air dryer).

D. Air dryer not purging (see Symptom #5).

E. Purge (air exhaust) time insufﬁ cient due

to excessive system leakage (see causes

for Symptom #1).

F. Air dryer/vehicle application requires

additional purge volume.

G. Air dryer is not compatible with the

vehicle air system requirement -

(Improper air dryer/vehicle application).

A. Desiccant cartridge plugged or saturated.

B. Defective check valve between air dryer

outlet port and ﬁ rst reservoir. (in standard

AD-2 air dryer, check valve in outlet port.)

C. Defective ﬁ ttings, hose or tubing between

air dryer and ﬁ rst reservoir.

Contact the Bendix Tech Team at 1-800-247-2725 (option 2)

or [email protected]. Representatives are available to

assist you Monday – Thursday, 8:00 a.m. – 6:00 p.m. ET

and Friday, 8:00 a.m. – 5:00 p.m. ET.

REMEDY

A. Test for excessive leakage and repair. Allowable

leakage:

• Pre-121 vehicles, single vehicle - 2 psi/minute.

• Tractor trailer - 3 psi/minute.

• 121 vehicles, single vehicle - 1 psi/minute per

service reservoir.

B. Using a soap solution, test for leakage at the ﬁ ttings,

drain valve (if any) and safety valve in the ﬁ rst

reservoir. Repair or replace as necessary.

C. Test the check valve. Leakage should not exceed a

1" soap bubble in 5 seconds. It may be necessary to

remove the air dryer check valve to test. Repair or

replace as necessary.

D. Test the governor for proper cut-in or cut-out

pressures and excessive leakage in both positions.

E. Remove the end cover. Apply 120 psi at the control

port. Soap both sides around purge valve to test for

control piston leakage. (Permissible leakage - 1"

bubble in 5 seconds.)

F. Remove the air strainer or ﬁ tting from the compressor

inlet cavity. With the compressor unloaded, check for

unloader piston leakage. Slight leakage is permissible.

A. Replace the desiccant cartridge.

B. Discharge Line Length:

• Minimum of 6' metal tubing for a two-cylinder

compressor.

• 10' for a one-cylinder compressor.

• ﬂ ex hose can be substituted at ratio of 1-1/2' ﬂ ex

hose for each 1' of metal.

C. If the system must have an outside air ﬁ ll provision,

the outside air should pass through the air dryer.

(Unused inlet on air dryer can be used.) Use of this

should be minimized.

D. See cause and remedy for Symptom #5.

E. Check causes and remedies for Symptom #1.

F. When compressor is loaded (compressing) longer

than 90 seconds during normal operation, additional

purge volume may be needed. (Before proceeding,

contact the Bendix Tech Team. See contact

information below.)

G. Air dryer requires minimum purge time of 30 seconds.

If the compressor stays loaded longer than 90

seconds and ad ditional purge volume is added,

longer purge time is re quired. Air dryer efﬁ ciency

will decrease as compressor loaded time increases

beyond 120 seconds, during normal operation of

the vehicle. (This limitation assumes a com pressor

of approximately 12 CFM and engine operation at

1600-1900 RPM.) The air dryer will accommodate

occa sional longer loaded times, such as the initial

system build-up.

A. Check compressor for excessive oil passing and/or

correct compressor installation. Repair or replace as

necessary. Rebuild or replace the cartridge.

B. Test to determine if air is passing through check valve.

Repair or replace.

C. Check to determine if the air is reaching the ﬁ rst

reservoir. Inspect for kinked tubing or hose. Check for

undrilled or restricted hose or tubing ﬁ ttings.