Table 4-1. TROUBLESHOOTING (cont.)

TM 5-4120-359-14

Table 4-1. TROUBLESHOOTING (cont.)

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

NOTE

During LOW HEAT operation only, one bank (nine) of the heaters are operational.

These heaters are thermostatically controlled by the TEMPERATURE CONTROL.

During HIGH HEAT operation an additional second bank (six) of heaters operate

continuously.

Step 2.

Check that TEMPERATURE CONTROL is set to WARMER position.

Set TEMPERATURE CONTROL to WARMER position.

Step 3.

Inspect fresh and return air filters for dirt or blockage.

Clan filter/remove blockage.

Step 4.

Check thermostatic switches S2 and S3. (See paragraph 4-29.)

Replace if found bad.

Step 5.

Check relays K4 and K5. (See paragraph 4-52.)

Replace if found bad.

Step 6.

Check temperature control A1. (See paragraph 4-47.)

Replace if found bad.

Step 7.

Check temperature sensing probe A1-RT. (See paragraph 4-20.)

Replace if found bad.

Step 8.

Check mode selector switch S1. (See paragraph 4-103.)

Replace if found bad.

Step 9.

Check electrical heating elements HR1-HR15. (See paragraph 4-31.)

Replace if found bad.

EVAPORATOR BLOWER MOTOR FAILS TO START.

(Compressor, condenser blower motor, and heaters start.)

Step 1.

Check relay K3. (See paragraph 4-52.)

Replace if found bed.

Step 2.

Check motor B3. (See paragraph 4-28)

Replace if found bad.

COMPRESSOR FAILS TO START

(Condenser blower motor does not start, evaporator blower motor starts.)

Step 1.

Check condenser safety circuit.

(a) Disconnect P14 connector.

Change 3 4-9