21
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.
Temperature (°F) Resistance (k
Ω
)
0
14.401
10
10.613
32
6.000
50
3.871
70
2.474
90
1.633
Check a thermistor for resistance by using the following procedures.
(i) Disconnect the connector K3 on the board.
(ii) Remove the Thermistor. See “V. 11. 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
Ω
. Replace the Thermistor if it exceeds the normal
reading.
2) Defrost Timer
No adjustment is required under normal use, as the Defrost Timer is adjusted to the
suitable position. However, if necessary when all the ice formed on the Evaporator
does not fall into the bin in the harvest cycle, adjust the Defrost Timer to longer setting
by adjusting the Dip Switch (No. 1 & 2) on the Controller Board.
SETTING
TIME
Dip Switch
Dip Switch
No. 1
No. 2
OFF
OFF
60 seconds
ON
OFF
90 seconds
OFF
ON
120 seconds
ON
ON
180 seconds
