TM 9-4120-399-14
Table 4-3. Unit Troubleshooting.
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Step 2.
Check operation of heater thermostat cut-out switch (S3).
Test and replace defective thermostat cut-out switch per para.
Step 3.
Check operation of mode selector switch.
Test and replace defective mode selector switch per para. 4-43.
7.
HEAT IN HI HEAT MODE, BUT NOT IN LO HEAT MODE.
Step 1.
Check for loose or damaged electrical connectors, or damaged wires
in wiring harnesses.
WARNING
Disconnect
i n p u t power before
internal
performing
electrical
troubleshooting. Voltages used can
be deadly.
Tighten or replace loose or damaged connectors, or repair damaged
wires.
Step 2.
Check operation of heater relay (K1).
Test relays. Replace relays if defective per para. 4-39.
Step 3.
Check operation of temperature control thermostat switch (S1).
Inspect sensing bulb and capillary for damage or leakage.
a.
Replace entire temperature control thermostat switch if bulb is
damaged or leaking per para. 4-43.
b. Test switch in temperature control thermostat switch. Replace
entire control if defective per para. 4-43.
Step 4.
Check operation of mode selector switch (S3).
Test and replace defective switch per para. 4-43.
4-31
