TM 5-4520-241-14
SECTION VII. MAINTENANCE OF CONTROL BOX ASSEMBLY
4-19.
DESCRIPTION.
heater, and may be rotated in 90 degree increments to correspond to the mounting position of the heater. The control box
houses the room thermostat receptacle and the circuit breaker. It also provides a cavity for the electrical components in
the control box cover.
b. Control Box Wiring Harness. This harness connects the electrical circuitry in the control box cover to a male plug.
This plug is inserted into a mating receptacle in the front of the heater case.
c. Control Box Cover. The cover contains a printed circuit board assembly and a transistor to simplify the circuitry of
the time delay mechanism. It also contains the indicator lights, the time delay assembly, and the HEATER-OFF-FAN
switch that controls the heater operation.
d. Time Delay Transformer. This unit is functionally part of the item delay assembly, but it is not located in the
control box. The transformer is just below the terminal board inside the right side access door.
4-20.
CONTROL BOX, ELECTRICAL RECEPTACLES, AND CIRCUIT BREAKER.
WARNING
This space heater contains dangerous voltages which can cause severe electrical
shock. Be sure to disconnect the power plug before repairing the heater.
a. Removal and Disassembly.
(1) Disconnect the power plug from the power plug receptacle.
(2) Open the control box cover and unplug the control box harness (2, fig. 4-15). Save gasket (1).
(3) Remove the control box from the heater by releasing the two stud assemblies (19).
(4) Remove nuts (3), lock washer (4 and 5), and screw (6) to remove the grounding leads.
(5) Remove nuts (7), lock washers (8), and screws (9) to separate the control box cover (10) from control box
weldment (23).
4-44