NO HEAT IN EITHER HI HEAT OR LOW HEAT MODE.

TM 5-4120-393-14

Table 4-2. Unit Maintenance Troubleshooting

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

Step 2.

Check fans for looseness or damage, and for rotational clearance.

Tighten loose fans, adjust for rotational clearance, or replace if damaged.

Step 3.

Check all internal components for looseness, vibration, and security.

Tighten, adjust, and secure as necessary.

9. NO HEAT IN EITHER HI HEAT OR LOW HEAT MODE.

Step 1.

Check for loose or damaged electrical connectors, or damaged wires in wiring harness.

WARNING

Disconnect input power before performing internal electrical troubleshooting.

Voltages used can be deadly.

Tighten or replace loose or damaged connectors, or repair damaged wires.

Step 2.

Check operation of heater thermostat (S3).

Test thermostat. (See para 4-57.) Replace thermostat if defective.

Step 3.

Check operation of mode selector switch (S).

Test switch. (S ee para 4-38.) Replace switch if defective.

10. 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 harness.

WARNING

Disconnect input power before performing internal 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 relay. (See para 4-43.) Replace relay if defective.

Step 3.

Check operation of TEMPerature control thermostat (S1).

a. Inspect sensing bulb and capillary for damage or leakage. Replace entire control if bulb

is damaged or leaking.

4-41