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Page Title:
Control Head Assembly (Liquid Heater) |
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 191. Defroster Switch
(1) Remove the control head cover. Depress
(fig. 71.27).
and turn the shield (4), then lift off. Pull
relay from the shield-type socket (2).
a. Removal. Disconnect the electrical leads from
the switch.
Remove the knob and retaining nut.
(2) To test the timing relay, apply proper
Remove the switch.
voltage across terminals 1 and 2 and
check continuity across terminals 6 and 9
b. Installation. Install in reverse of removal.
(fig. 71.7 for method of determining
terminal numbers).
Within 30 to 60
192. Control Head Assembly (Liquid Heater)
seconds, the circuit through terminals 6
(fig. 71.28).
and 9 should open. Continuity should now
Most of the parts of the control head assembly
be between terminals 4 and 6. Replace a
can be replaced by merely removing the cover and
faulty relay; do not attempt to adjust or
disconnecting the part. Refer to paragraph 194b if
repair it.
complete removal is required.
(3) Either relay can operate in either socket.
a. Lower Delay.
If the operation of the preheat relay is
(1) The power relay controls the circuits to
suspected, interchange it with the nonfire
the fuel regulator valve, combustion
relay and operate the heater. If ignition
blower motor, ignition system, and the
takes place, the relay originally in the
nonfire relay. A defective power relay
preheat circuit is defective. If ignition
would affect operation of the heater
does not take place, continue testing the
beyond the preheating cycle.
relays and the other circuits.
(2) Remove the power relay (9, fig. 71.28) by
c.
Ignition Coil Assembly (fig. 71.28).
pulling it from the socket (11).
(1) If ignition troubles occur, inspect the
(3) To test, apply nominal voltage to
ignition coil assembly (25) for a corroded
terminals 2 and 7 (fig. 1.7 for method of
high-tension terminal socket or a crazed
determining terminal numbers); the
high-tension cable. Test the coil with
contacts should close immediately. Use
standard coil testing equipment, using
an ohmmeter to check continuity between
voltage stamped in the coil case. If it is
contacts 1 and 3, 4 and 5, and 6 and 8,
defective, replace the coil.
Do not
when the relay is energized. Replace a
attempt to repair a faulty coil.
faulty relay; do not attempt to adjust or
(2) To replace the ignition coil assembly (25),
repair it.
loosen the clamp that secures the shield
b. Preheat and Nonfire Relays (fig. 71.28). The
(15) to the ignition coil, remove the shield,
preheat relay and the nonfire relay (3) are identical
and disconnect the wires. Loosen the
timing relays effective during different cycles of heater
screw on the coil mounting clamp (16);
operation. Remove and test the relays as follows:
remove the coil assembly. When
1
Screw
11
Socket
21
Connector
2
Socket
12
Spacer
22
Screw
8
Relay
13
Base
23
Screw
4
Shield
14
Nut
24
Grommet
5
Screw
15
Shield
25
Coil
6
Terminal block
16
Clamp
26
Nut
7
Resistor
17
Tee
27
Base assembly
8
Nut
18
Elbow
28
Grommet
9
Relay
19
Valve
29
Screw
10
Screw
20
Base
Figure 71.28. Control head assembly.
AGO 5667A
26
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