TM 5-4520-241-14
Table 5-1. Direct Support and General Support Troubleshooting - Continued
MALFUNCTION
TESTING OR INSPECTION
CORRECTIVE ACTION
1 - Continued
Connect the power plug. Press the RESET button to clear the switch. Using a stopwatch or a
clock with a sweep second hand, move the HEATER-OFF-FAN switch to HEATER and start timing.
The bimetallic heater-sensor must trip the RESET switch within 60 to 90 seconds at an ambient
temperature between 65 and 75 F (18 to 24C). If the time delay operates within this range, no
adjustment is required. Reconnect the wires and go to step 3.
If the time delay is outside the specified range, adjust the bimetallic heater/sensor by turning the
slotted head screw that moves the end of the sensor closer to or farther from the reset switch. If
the time delay was too short, turn the screw counterclockwise 1/4 turn, and retest as described
above. If the time was too long, turn the screw clockwise 1/4 turn and retest.
When the adjustment is correct, turn off the power and disconnect the power plug. Reconnect
the brown lead to terminal G, and the yellow lead to the electrical connector. Close the control
box cover. Check the beater for proper operation.
Step 3.
Inspect the burner head. Disconnect the power plug and open the access doors. Disconnect the
ignition cable from the igniter, and remove the igniter from the burner head. Disconnect the fuel
lines at the elbows on the carburetor. Remove the screws securing the carburetor to the burner
head. Pull off the carburetor and move it out of the way. Remove the five screws that secure the
burner to the heat exchanger. Pull off the burner and gasket. Inspect the burner head for
combustion deposits or debris clogging the combustion air inlet or igniter hole. Check that all
internal baffles are in good condition and are securely welded to the burner head. Check for
excessive buildup of carbon in the heat exchanger.
5-3
