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90 Combustion abnormality
Only connect and disconnect the connector after the fan has
stopped rotating and then disconnect the electrical power.
(The Circuit Board and Fan Motor may be damaged otherwise.)
Check the Dip Switch settings.
Normal
Check whether the burner gas pressure is normal.
Normal
* Check the primary pressure (dynamic pressure) at the time of maximum capacity combustion.
Check whether the burner gas pressure is normal.
Normal
Abnormal
Check whether the burner gas pressure can be adjusted.
Check for clogging of the heat exchanger,
deformation or clogging of fan blades, etc.
Check the carry over of burners.
Normal
During combustion, change the
hot water temperature and
water flow, and through the
peephole of the burner, check
that the number of burners
ignited switches normally.
A
Abnormal
Normal
Abnormal
Check the voltage of the Gas Proportioning Valve.
Normal
CN 101: between Red 7 - Blue 6
* When adjusting
the gas burner
BL
R
pressure, the
W
voltage change
O
10
within the range
DC 0.3 - 15V.
<CN101>
Normal
Abnormal
Check the voltage of Gas Solenoid Valve-2
(SV2), Gas Solenoid Valve 3(SV3) and
Gas Solenoid Valve 4(SV4).
Normal
During combustion, press the "maximum or minimum burner
pressure set button", and check check the volltage below.
(SV2)
CN10 : Gray 8 - Blue 6
1
DC 14 - 16V
1
2
3
3
1
2
<CN10>
<Condition of occurrence for error code 90>
"Output/FF+FB No.
(Maintenance No.52 / Maintenance No. 51
Abnormal
Abnormal
Circuit Board
<CN42>
6
1
R
W
4
1
BK
7
2
BL
5
2
<CN101>
6
3
8
3
G
BL
6
1
R
R
7
2
BL
9
4
W
W
8
3
G
9
4
W
5
Y
O
10
5
Y
1
BK
2
3
W
4
5
W
6
BL
7
BR
8
GY
9
BK
10
O
11
12
W
<CN10>
Abnormal
Abnormal
(SV3)
CN10 : Orange 10 - Blue 6
2
DC 14 - 16V
Circuit Board
<CN42>
W
4
1
BK
5
2
<CN101>
1
6
3
BK
BL
6
1
R
R
7
2
BL
2
W
8
3
G
3
W
9
4
W
O
10
5
Y
4
1
BK
5
W
2
3
W
6
BL
4
5
W
7
BR
6
BL
7
BR
8
GY
8
GY
9
BK
9
BK
10
O
10
O
11
12
W
11
<CN10>
12
W
- 41 -
50%"
To correct the setting
Check the gas supply
valve, etc.
Primary gas pressure list
Gas group
Pressure
Maximum
kPa
pressure
Minimum
kPa
pressure
Replace the Circuit Board set.
<CN186>
1
MAIN
2
3
CIRCUIT
4
5
BOARD
6
W
31
32
R
29
30
V
27
28
BK
O
25
26
G
W
23
24
BK
21
22
19
20
V
BL
17
18
G
O
15
16
O
1
W
13
14
BL
2
W
11
12
3
W
9 10
Y
4
7 8
R
W
1
BL
5 6
5
W
Y
Y
2
BL
6
W
R
3 4
BK
3
BL
7
W
1 2
W
<CN63>
<CN38>
<CN89>
Check for improper connection of wiring,
then replace the Gas Valve.
Inspect for clogging of the heat exchanger,
abnormality of fan blades, etc.
Adjust the burner gas pressure to a correct value.
Replace the Circuit Board set.
(SV4)
CN10 : Brown 7 - Blue 6
3
DC 14 - 16V
<CN186>
1
MAIN
2
3
CIRCUIT
4
5
6
BOARD
W
31
32
R
29
30
V
27
28
BK
O
25
26
G
W
23
24
BK
21
22
19
20
V
BL
17
18
G
O
15
16
O
1
W
13
14
BL
2
W
11
12
3
9 10
Y
W
7 8
4
W
R
1
BL
5
W
Y
5 6
Y
2
BL
6
W
R
3 4
BK
3
BL
7
W
1 2
W
<CN63>
<CN38>
<CN89>
Check for the orifice clogging of Manifold,
then replace the Manifold that does not
open.
50%)
UPLG
NG
3.5
3.0
2.75
1.13
R
BK
W
G
BL
BL
1
BL
2
<CN78>
1
2
3
BK
<CN197>
R
BK
W
G
BL
BL
1
BL
2
<CN78>
1
2
3
BK
<CN197>
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