TABLE 4-2. TROUBLESHOOTING - continued

TM5-4120-347-14

TABLE 4-2. TROUBLESHOOTING (cont.)

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

Step 5.

Check continuity across primary winding and across secondary winding of control transformer

to see whether windings are good. (See figure 4-38.)

Replace bad transformer. (Refer to paragraph 4-38.)

Apply 30 volts a-c across side terminals; check for 24-28 volts d-c across end terminals

Step 6.

(marked + and -) of rectifier.

Replace bad rectifier. (Refer to paragraph 4-38.)

Step 7.

Observe operation of time delay relay.

Replace bad relay. (Refer to paragraph 4-35.)

Step 8.

Substitute compressor relay known to be good, and check operation.

Replace bad relay. (Refer to paragraph 4-35.)

Substitute starting relay or capacitor known to be good and check operation.

Step 9.

Replace bad capacitor or relay. (Refer to paragraph 4-14.)

Step 10. Tape an accurate thermometer or thermocouple to the discharge tube of the compressor, and

check for too high an operating temperature which would trip the compressor's internal

temperature overload switch.

Let compressor cool. Report fault to direct support maintenance if condition continues.

Step 11. Test compressor motor by checking continuity of the following pins at the compressor electri-

cal receptacle (See figure 4-5 for pin identifications).

(1) Pins A and B, B and C, and C and A. Continuity should exist.

(2) Pins A, B and C and compressor housing. No continuity should exist.

(3) Pins D and E. Continuity should exist when compressor is cool enough for internal

thermostat to be closed. If compressor is hot, let cool and retest.

Report faulty motor to direct support maintenance.

COMPRESSOR STARTS, BUT GOES OUT ON OVERLOAD.

Step 1.

Observe condenser fan motor for failure.

Replace bad motor. (Refer to paragraph 4-43.)

Step 2.

Check for high head pressure.

Clean condenser coil and louvers. Check fan for proper operation.

EVAPORATOR AIR OUTPUT VOLUME LOW.

Step 1.

Check for dirty or damaged filter or louvers.

Clean or replace filter. Clean or replace louvers as required.

Step 2.

Check for dirty or iced evaporator coil.

De-ice and clean coil.

Step 3.

Inspect evaporator fan for damage.

Replace fan. (Refer to paragraph 4-40.)

Step 4.

Check for bad fan motor.

Replace motor. (Refer to paragraph 4-40.)

Step 5.

Check to be sure that evaporator fan speed switch is not set at low speed.

Reset switch to high speed.

CONDENSER AIR OUTLET VOLUME LOW.

Step 1.

Check for dirty condenser coil or guard.

Clean coil and guard.

Step 2.

Check for bad high-low condenser fan thermostatic switch, using lamp bulb or heat gun and

ohmmeter to check continuity.

Replace bad switch. (Refer to paragraph 4-39.)

4-23