Electrical Diagnostic Points
Wire Color
Voltage
Resistance
Connector No. Pin No.’s
(SV1, SV2, SV3, POV) Gas Valve and Modulating Solenoids
(Main) Pink - Black
11 - 13 VDC
36.8 - 44.8 ohms
H5
6 ~ 7
6
~
5
6
H
w
o
ll
e
Y
-
k
c
a
l
B
)
1
V
S
(
6
~
4
7
H
e
u
l
B
-
k
c
a
l
B
)
2
V
S
(
6
~
3
8
H
n
w
o
r
B
-
k
c
a
l
B
)
3
V
S
(
(POV) Pink - Pink
2 - 15 VDC
67 - 81 ohms
H3
9 ~ 10
(M) Water Flow Servo
Red - Blue
11 - 13 VDC
22 - 26 ohms
F7
9 ~ 10
Gray - Brown
4 - 6 VDC
N/A
F7
5 ~ 7
Gray - Yellow
N/A
N/A
F7
5 ~ 8
NOTE: At the F connector on the PCB: gray wire turns to black, orange wire turns to red
(QS) Water Flow Sensor
Black - Red
11 - 13 VDC
5.5 - 6.2 K ohms
F2
1 ~ 3
Yellow - Black
4 - 7 VDC
1 - 1.4 mega ohms
F2
2 ~ 3
Bypass Flow Control
(only on 505e/o and 505i)
Brown - White
2 - 6 VDC
(unit in operating
mode)
15 - 35 K ohms
G1
1 ~ 5
5
~
2
e
ti
h
W
-
e
g
n
a
r
O
5
~
3
e
ti
h
W
-
w
o
ll
e
Y
5
~
4
d
n
u
o
r
G
/
e
ti
h
W
-
d
e
R
(IG) Ignition System
Gray - Gray
90 - 110 VAC
N/A
C1
1 ~ 2
(FM) Combustion Fan Motor
Red - Black
6 - 45 VDC
N/A
E1
1 ~ 2
White - Black
5 - 10 VDC
9.2 - 9.4 K ohms
E1
2 ~ 4
Yellow - Black
11 ~ 13 VDC
3.5 - 3.9 K ohms
E1
2 ~ 3
With the meter set on hertz scale, 60-420 hertz should be across the red and yellow wires at
terminals 2 and 4.
On-Demand Gas Tankless Water Heater Service Manual
13
305e/o, 305i, 505e/o, 505i
