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TM 9-4120-367-14
TM 07592B-14/1
Table 4-3. Electrical Components Tests - Continued
No.
2
3
4
5
6
7
8
9
Procedure
Time Delay Relay K1. Apply 28 volts DC to terminals 2 and 5: positive to terminal 2
and negative to terminal 5. Check across terminals 2 and 3 to see that contact is made
within 30 ± 3 seconds of energizing the coil. Replace defective relay. See paragraph
5.9.
Relay K2 and K3. Test each relay in the same manner. Apply 28 volts DC to terminals
X1 and X2: positive to X1 and negative to X2. Check continuity of pairs: A1 - A2, B1 -
B2, and C1 - C2. Replace defective relay. See paragraph 5.10.
Relay K4. Relay K4 is an 11 pin continuous duty, three pole, double throw, 24 volt DC
coil relay. When the coil is activated by thermostatic switch S7, contacts 1 - 3, 5 - 11,
and 10 - 8 open and terminals 1 - 4, 5 - 6, and 10 - 7 close. See paragraph 5.8.
NOTE
Pins 5 - 6 and 5 - 11 are not used in single-phase unit model F18H.
Apply 28 volts DC to terminals 2 and 9: positive to terminal 2 and negative to terminal 9.
Check continuity. Terminals (contacts) 1 - 3, 5 - 11, and 10 - 8 should be closed; 1 - 4,
5 - 6, and 10 - 7 should be open. Remove the power. Terminals 1 - 4, 5 - 6, and 10 -7
should be closed; 1 - 3, 5 - 11, and 10 - 8 should be open. Replace defective relay.
Transformer T1. Apply 115 volts AC, 120 watts, to input terminals 1 and 2 (F18H,
F18H-3, or F18H-4) or 2 and 5 (F18H-3A, F18H-4A, or MHP-20-4-08). Voltage at out-
put terminals 3 and 4 (F18H, F18H-3, or F18H-4) or 7 and 8 (F18H-3A, F18H-4A, or
MHP-20-4-08) should be 28 to 30 volts AC, 4 amps. Remove power from transformer.
Replace defective transformer. See paragraph 5.7.
Rectifier CR1. Apply 28 - 30 volts AC to rectifier terminals 1 and 3. Output at terminals
4 and 2 should be 26 to 30 volts DC. Terminal 4 is negative and terminal 2 is positive.
Replace faulty rectifier. See paragraph 5.6.
Mode Selector Switch S1. Check continuity of selector switch in all positions. See table
4-4 or table 4-5. See paragraph 5.11.
Temperature Selector S3. Remove the return air louver and air filter. Carefully remove
the sensing bulb from the damped position. Place the sensor bulb in a container of
warm water 85°F to 100°F (30° to 40°C). Turn knob from the extreme WARMER to
extreme COOLER position. Continuity should be indicated. See paragraph 5.12.
Place the sensor bulb in a container of cold water 40° to 65°F (5° to 18°C). Turn the
knob from the extreme COOLER to the extreme WARMER position. Continuity should
be indicated.
Fan Speed Switch S2 (all models except MHP-20-4-08). Check continuity in both posi-
tions. Continuity should be indicated. See paragraph 5.13.
4-4
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