Noritz NR501-OD Service Manual page 51

A
Check the actual output.
Normal
Should be maintenance monitor
#51 (FF + FB No.) x 50% < #52 (Output) data.
Check whether the Thermistor-Cold Water and Thermistor-Hot Water are normal.
Normal
Disconnect electrical power,
(pass through the water to the Unit.)
e, and then reconnect electrical power.
Check the maintenance monitor.
The difference between # 30 (Cold Water ) and # 31
(Hot Water) should be within ±5 ˚ F.
Check the thermistor resistance.
Normal
1
CN63 White 4 - Black 2 (Cold Wa ter)
2 CN63 White 1 - Black 2 (Hot Wa ter)
Refer to the thermistor temperature
characteristics below.
Circuit Board
14
13
14
13
12 BL
12 BL
11 W
10 R
9 Y
11 W 8
7
6 BK
10 R 5 BK
4 W
3 W
2 BK
9 Y
1 W
<CN63>
8
<CN135>
7
<CN78>
6 BK
2
1
1 BL 2
5 BK
3
BL
4 R
5 W
4 W
6 O
7 GY
8 BK <CN10>
3 W
9
10 W
11 BL
2 BK
12
6 BK 13 W
14
5 R
1
W
15 BL
4
3
2 W
1 W
<CN42>
<CN63>
51
Abnormal
Abnormal
Abnormal
Check for improper connection of wiring,
connectors, etc., then replace the thermistor.
When measuring the resistance,
disconnect the connector and check
the male side.
12 W
11 Y
10 O
9 R
8
7
Main
6 BK
5 V
Circuit
4 G
3 O
Board
2 Y
1 W
<CN59>
1
2
1 2 3
3 4 3 2 1
4 BL
4 R
3 BL BR Y BL R
5 O
2 BL
6 Y <CN27>
1 R
7 W
<CN142>
Po wer
<CN104>
Circuit
3 R
Board
2 BL
1 G
<CN101>
<CN89B>
3
2
1
<CN75>
3 2 1
BL/W R/R G
<CN102>
<CN89A>
Replace the Circuit Board set.
* It is not necessary to replace the
Displ ay Window Circuit Board.
Check for clogged w
then replace the Water Flow Sensor.
Replace the Circuit Board set.
* It is not necessary to replace the
Displ ay Window Circuit Board.
Displ ay Window
Fuse
Circuit Board
Data
Display
W 3 1 W
BK 4 2 BK
<CN92>
Dip Switch
1 2 3 4
R BL BL BL
<CN142>
s,