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4. Service procedures
Check Pin
Short-circuit the cooling check pin (or heating check pin) on the outdoor unit control PCB to perform the control
described below.
1. Thermistor checks
The checks listed below are performed for 1 second each, in order from the top down. The results are displayed
by LED 1 and 2.
Discharge temp. (TD)
Outdoor air temp. (TO)
Heat exchanger temp. (C1)
Heat exchanger temp. (C2)
Intake temp. (TS)
Thermistor
Check results
Normal Abnormal
LED 1 and 2 OFF
LED 1 lit
LED 1 lit
LED 1 lit
LED 2 lit
2. 4-way valve turns ON for 1 second.
3. Forced cooling (or heating) operation
4-4. Table of Thermistor Characteristics
(1) Outdoor Air Temp. (TO), Intake Temp. (TS), Heat
Exchanger Temp. (C1) Sensor, Heat Exchanger
Temp. (C2) Sensor
(2) Discharge Temp. (TD) Sensors
Temperature (˚F)
Resistance (kΩ)
Temperature (°F)
Resistance (k
Ω)
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