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TM 9-4120-367-14
TM 07592B-14/1
No.
10
11
12
13
14
Table 4-3. Electrical Components Tests - Continued
Procedure
Motors B2 and B3. Disconnect power from the unit. Spin the fan/blower. Listen for
bearing noise. If bearing noise is evident, turn shaft slowly backward and forward to
check for roughness. Use multimeter and check that no continuity exists between each
pin and motor frame. Replace defective motor. See paragraph 6.29.
Relay K5. (Single phase only.) Apply 230 volts single phase, 60 Hertz to terminals 1
and 5. Contact which is across 1 and 2 should open at voltage rise between 180 to 190
volts. Remove voltage. Contact should dose upon voltage drop between 115 and 55
volts. Rating of relay is 5180 ohms. See paragraph 5.18.
Condenser Fan Switch S7. Tape the bulb of a thermometer or junction of a thermocou-
ple to the sensing part of the switch. Disconnect plug P7 and connect multimeter to the
connector. Gradually apply heat and observe both the thermometer and multimeter.
Contact shall be open until temperature reaches 100°F (38°C) and above, at which
time contact should close. Allow temperature to drop. Contact should open at below
100°F (38°C). Remove meter and connect plug. See paragraph 5.27.
Hester Thermostat S6. Visually inspect the heater thermostat for crack in the housing,
missing pieces or other damage. Replace. See paragraph 5.28.
a.
b.
c.
d.
Using a multimeter, check continuity of the wire leads attached to terminals 1 and 2,
and 3 and 4 of the heater thermostat. Continuity should be indicated.
Tape the bulb of a thermometer or junction of a thermocouple to the body of the
heater thermostat, and leave the continuity tester connected to terminals 1 and 2.
Gradually apply heat, and observe both the thermometer and the continuity tester.
Continuity should drop out at 194° ± 9°F (90° ± 5°C). While still continuing to
watch the thermometer end the continuity tester, let the heater thermostat cool. Con-
tinuity should be re-established at 142° ± 17°F (61° ± 9°C).
Repeat Step b. with the meter connected to terminals 3 and 4.
If the heater thermostat does not meet temperature and continuity requirements,
replace it.
Heater HR1 through HR6. The six steel sheathed resistance heating elements are lo-
cated immediately behind the evaporator coil and extend all the way across the width of
the evaporator. Three of the elements are energized when the selector switch is set at
LOW HEAT, and all six elements are energized when the selector switch is set at HIGH
HEAT. The temperature control thermostat controls only the elements energized by the
LOW HEAT setting. All six elements are protected against overheating by a thermal
overload protector (heater thermostat). See paragraph 5.29.
4-5
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