Service manual

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(2) Measure the voltage between Red 1 and Blue
7 of connector 75 on the circuit board.
3. Water inlet thermistor error.
(1) Measure the resistance between White 1 and
White 3 of connector Q63.
If error display 31 appears, then make sure the water
inlet thermistor and the temperature shown in
maintenance information monitor no. 30 match.
Normal DC 14 - 16V
No Replace the circuit board.
Break in wire: ∞Ω
Short circuit: 1Ω or less
If wire is broken or short-circuited, replace the
water inlet thermistor.
If the problem is not a broken or short-circuited
wire, then inspect/repair the wirings/connectors
of the water inlet thermistor.
2. Error display 20 immediately after turning unit
ON.
Inspect the high-limit switch.
(1) Remove connector 1 and connector 92 on the
circuit board and measure the resistance
between Black 3 of connector 1 and White 6
of connector 1.
Normal 1Ω or less
Yes Replace the circuit board.
No
After finding the cause, restore/replace
the high limit switch.
Yes Replace the water flow sensor.