Thermo King SLXi Spectrum, Maintenance Manual

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Structural Maintenance 12-21
Testing the Damper Motor Heater
1.
• Units with TG-V: Disconnect the thermostat switch wire from the 7K wire in the evaporator wire harness.
• Units with TG-VI, µP-IV, µP-V, µP-VI or SR-2: Disconnect the damper motor connector from the evaporator harness.
2.
• Units with TG-V: Check the resistance between the thermostat switch wire and CH.
• Units with TG-VI, µP-IV, µP-V, µP-VI or SR-2: Check the resistance between pins 3 and 4 in the 6-pin connector on the
damper motor.
a. When the temperature of the thermostat switch is above 2 C, there should be no continuity between the thermostat switch
wire and CH (or pins 3 and 4). If there is continuity, the thermostat switch is defective.
b.When the temperature of the thermostat switch is below -16 C, the resistance between the thermostat switch wire and CH
(or pins 3 and 4) should be approximately 12 ohms. If not, check the switch and the resistance wire separately.
3. To check the switch and resistance wire separately, cut the splice connector that connects the switch wire to the resistance
wire.
4. Check the resistance wire by checking the resistance between the end of the resistance wire and CH (or pin 4). The resistance
should be approximately 12 ohms. If not, the resistance wire is defective.
5. Check the thermostat switch by checking the resistance between the switch wires (or switch and pin 3).
a. When the temperature of the thermostat switch is above 2 C, there should be no continuity through the switch. If there is
continuity, the thermostat switch is defective.
b.When the temperature of the thermostat switch is below -16 C, there should be continuity through the switch. If not, the
thermostat switch is defective.
Damper Motor Heater – SMX (After 5/93), SMX-II
and SL
1. Thermostat Switch
2. Thermostat Switch Wires
3. Resistance Wire
4. Diode
5. Pin 3 (CL Wire)
6. Pin 4 (Resistance Wire)
7. CL Wire
8. Resistance Wire