TM 5-4520-253-13
Table 3-3. Unit Maintenance Troubleshooting – Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Step 6. Check HEATER-OFF-FAN switch.
Disconnect power cable, open control box,
and check for continuity as follows:
a.
b.
c.
Between terminals (6 and
1), switch in FAN
position.
Between terminals (3 and
2), switch in FAN
position.
Between terminals (3 and
4), switch in HEATER
position. Terminal (5) is
not used in this appli-
cation.
Replace defective switch
as described in lNSPECT/
TEST/REMOVE/lNSTALL
HEATER-OFF-FAN
SWITCH, page 3-55.
2. HEATER FAILS TO START WHEN SWITCH IS SET
LIGHT OFF.
Step 1. Check room thermostat setting for
low temperature adjustment.
Set room thermostat temper-
ature adjustment knob to at
least five degrees above room
temperature.
Step 2. Check for defective room thermostat.
Place HEATER-OFF-FAN switch in
OFF position.
Remove room ther-
mostat cover. Set temperature
adjustment knob to maximum and
check for continuity between
terminals.
TO HEATER, WHITE LIGHT ON, RED
If no continuity, disconnect 3-wire, 16-gauge, shielded cable. Remove
thermostat and replace as described in TEST/ADJUST/REMOVE/lNSTALL
ROOM THERMOSTAT, page 3-120.
3-27
