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3/8" bolts require replacement, insure that the
replacement bolts are grade 5 minimum and the same
length as the original bolts. Use of inferior bolts can
compromise the integrity of the air dryer and lead to
premature failure. Where a lower, right angle mounting
bracket (instead of a lower mounting strap) is used; line
up the marks made on the outer housing and end cover.
Install the six (standard) 3/8" cap screws, lock nuts and
twelve special washers. The two longer 3/8" cap screws
™
will be used to secure the AD-4
air dryer to the right
angle mounting bracket.
Note: If during the Operation & Leakage Tests it was
determined that the thermostat was inoperative, use the
following procedure for repair or replacement. It is not
necessary to replace this unit each time the end cover
is rebuilt. Use thermostat maintenance kit 102657 for
single terminal application. For dual terminal application,
use kit #103982. (See Figure 5.)
THERMOSTAT DISASSEMBLY
(Refer to Figures 5
and 8)
1. Remove nut (2), then lockwasher (3), plain washer (4),
nut (2) and o-rings (5). Discard o-ring and retain other
parts.
2. Remove and retain four Phillips head screws (7) and
cover (6).
3. Remove and discard gasket (10).
4. Remove and retain spacer (11).
HEATER
DELIVERY
2
VOLTS/WATTS
PORT
EMBOSSED
SAFETY
6
HERE
VALVE
CONTROL
PORT
4
5
SUPPLY
PORT
1&9
3
7
8
MOUNTING
HOOK
BRACKET
™
FIGURE 8 - AD-4
AIR DRYER END COVER WITH TORQUE
PATTERN
5. Cut uninsulated thermostat wire at Point B, remove and
discard thermostat and terminal assembly (1).
6. Clean remaining wire attached to heater terminal.
7. Clean thermostat “pocket” in end cover (9).
THERMOSTAT ASSEMBLY
(Refer to Figure 5)
1. Cut uninsulated lead of new thermostat (1) at Point A.
2. Install thermostat in end cover pocket and position
uninsulated leads next to each other.
3. Using a soldering heat sink, clamp uninsulated leads at
Point B and solder leads with straight rosin core solder.
Do not use acid core solder as corrosion can result.
Clean excess solder off end cover.
4. Install thermostat terminal (1) in cover (6).
5. Install o-ring (5), washer (4), and nut (2). Torque nut to
20-30 inch pounds. Then install lockwasher (3) and nut
(2) finger tight to allow for reconnection of electrical wire
when reinstalled on vehicle.
6. Install spacer (11) over thermostat (1).
7. Install gasket (7) and thermostat cover (6) and secure
thermostat cover to end cover (9) using screws (7) and
lockwashers (8).
8. Torque to 20-30 inch pounds.
9. Test thermostat as follows:
A. At a temperature above 90 degrees Fahrenheit,
check resistance between thermostat terminal (1)
and end cover (9). Resistance should be 1,000 ohms
or greater; if not, check for solder “path” short.
B. Chill entire end cover assembly to 40 degrees
Fahrenheit or below and check resistance again.
Resistance should be 2-4 ohms for a 12 volt, 60 watt
end cover and 4-7 ohms for a 24 volt, 120 watt end
cover.
UNLOADER
“UNL”
GOVERNOR
PORT
RESERVOIR
“RES”
COMPRESSOR
PORT
™
AD-4
AIR
SUP
DRYER
CON
SUPPLY
8-10 AMP FUSE
DEL
RESERVOIR
TO IGNITION
™
FIGURE 9 - AD-4
AIR DRYER INSTALLATION SCHEMATIC
Page 10
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Troubleshooting
