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1) Defrost Control
A thermistor (Semiconductor) is used for a defrost control sensor. The resistance var-
ies depending on the Suction Line temperatures. The Thermistor detects the tempera-
ture of the Evaporator outlet to start the Defrost Timer. No adjustment is required. If
necessary, check for resistance between Thermistor leads, and visually check the
Thermistor mounting, located on the Suction Line next to the Evaporator outlet.
Check a thermistor for resistance by using the following procedures.
(i) Disconnect the connector K3 on the board.
(ii) Remove the Thermistor. See "V. 10. REMOVAL AND REPLACEMENT OF THER-
MISTOR."
(iii) Immerse the Thermistor sensor portion in a glass containing ice and water for 2 or 3
minutes.
(iv) Check for a resistance between Thermistor leads.
Normal reading is within 3.5 to 7 K ohms. Replace the Thermistor if it exceeds the
normal reading.
Switch Nos. 9 and 10:
Temperature
°F
°C
0
-18
10
-12
32
0
50
10
70
21
90
32
Used for adjustment of Freeze Timer.
The Freeze Timer determines maximum
freeze cycle time. Upon termination of
Freeze Timer, machine initiates the
harvest cycle. After 2 consecutive timer
terminations, machine will shut down,
possibly indicating a problem.
Resistance (K ohms)
14.401
10.613
6.000
3.871
2.474
1.633
31
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