BENDIX AD-1 Service Data - Seite 6

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Note: Purge valve will be open when governor cut-out

pressure is reached. Allow two minutes for purge cycle

before testing the check valve.

4. Check for excessive leakage at the purge valve by

coating the exhaust with a soap solution while the

compressor is loaded (compressing air).

5. 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.

6. Check all lines and ﬁ ttings leading to and from the air

dryer for leakage and integrity.

7. 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 control "on", check

for power at the dryer's electrical terminal with a

voltmeter or test light. (See Figure 16.) If there is

no voltage, look for a blown fuse, broken wires, or

corrosion in the vehicle wiring harness.

B. Thermostat and Heater

1. Turn off the ignition switch and cool the

end cover assembly to below 40°F. With an

ohmmeter, check the resistance between the

electrical terminal and the aluminum of the end

cover. (See Figure 16.)

This resistance should be 2.0–4.0 ohms for a

12 volt end cover; 8.1–13 ohms for a 24 volt / 60

watt end cover; and 4.0–7.0 ohms for a 24

volt /120 watt end cover.

2. Warm the end cover assembly to over 90°F and

check the resistance as above. This resistance

should exceed 1,000 ohms.

If these resistances are within the limits, the

thermostat and heater are operating properly.

If these resistances are outside the limits,

proceed to Step C to determine the cause.

C. Heater Element

With the ignition or engine control switch "off",

remove the thermostat cover. (See Figure 17.)

With an ohmmeter, check the resistance between

the aluminum of the end cover and the heater post.

For a 12 volt end cover, the resistance should be

2.0–2.8 ohms. For a 24 volt / 60 watt end cover,

8.1–11.1 ohms; and for a 24 volt / 120 watt end

cover, 4.0–4.6 ohms. If the heater resistance is

outside these ranges, a new or remanufactured end

cover should be installed, since the heater element

cannot be serviced.

If the heater resistance is within the limits the

thermostat should be replaced (Kit Number

102657N) or a new or remanufactured end cover

installed.

D. Reassembly

Reinstall the thermostat cover as shown in

Figure 17. Use care to ensure the rubber spacer

and the gasket are correctly installed.

8. Every 7,200 hours, 200,000 miles, or every 24 months,

change the desiccant cartridge.

NOTE: The desiccant change interval may vary from

vehicle to vehicle. Although typical desiccant cartridge

life is two years, many will perform adequately for three

to four years. In order to take maximum advantage of

desiccant life and ensure that replacement occurs only

when necessary, it is important that Serviceability Checks

1–7 be performed.

REPLACING OR REBUILDING THE BENDIX

AD-1

™

AND AD-2

AIR DRYER

GENERAL

If, after completing the routine serviceability tests, it has

been determined that one or more components of the air

dryer requires replacement or maintenance, refer to page

13 to identify the appropriate kit(s) needed. When rebuilding

or replacing components of the air dryer, use only genuine

Bendix

replacement parts or kits.

REMOVAL OF THE DESICCANT CARTRIDGE

1. Loosen the air line to the control port of the air dryer

and allow the trapped air to escape to atmosphere.

After the air escapes, remove the control line from the

air dryer.

2. Loosen the delivery line from the delivery port or outlet

of the air dryer. After the pressure drops, remove the

delivery line. Loosen the delivery check valve from

this port to relieve any trapped air above the desiccant

plate assembly. If the AD-1 air dryer has an external

check valve at the delivery port, loosen it to relieve air

pressure.

3. Disconnect the heater wire.

4. Remove any exhaust silencers or the exhaust check

valve cover from the base of the air dryer. Using a hex

socket and wrench, loosen the purge valve assembly

and allow any trapped air to escape. Slowly unscrew

the purge valve and remove it.

5. Check all ports to ensure that air is not trapped in the

air dryer by powdered desiccant material.