TM 5-4520-241-14
Table 4-2. Organizational Maintenance Troubleshooting - Continued
MALFUNCTION
TESTING OR INSPECTION
CORRECTIVE ACTION
2 - Continued
room thermostat.
Step 4.
Check for defective room thermostat. Disconnect room thermostat cable from control box. Check
continuity across thermostat. Remove cover from room thermostat and check continuity across
switch terminals while rotating thermostat knob.
Replace thermostat if switch fails to open and close in response to rotating knob and rising and
falling temperature.
3.
VENTILATING MOTOR FAILS TO STOP AFTER HEATER HAS COOLED.
Step 1.
Check flame switch. Open access doors with power plug connected. While heat exchanger is hot,
and switch is OFF, check voltage at terminals C and G on terminal strip near carburetor.
If 120 volts is present on terminals, flame switch is defective.
Disconnect power plug.
Disconnect wires at flame switch, (8, fig. 4-4). It is normally possible to remove the flame switch
without removing the carburetor or burner head. Remove screws (1), washers (2 and 3), and pull
out assembled switch and bracket (4 through 8). Remove screws (4) and washers (5 and 6)
securing flame switch (8) to mounting base (7). Pull off defective switch. No repair is possible.
Install a new switch by reversing the removal procedure. Be sure tip of flame switch probe
engages bracket on heat exchanger.
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