Rheem 874W27NF Service Manual page 21

Diagnostic Points on Printed Circuit Board
Measurement Point
No. Connection
1 A
2 T
3 S
4 J
5 P
6 P
7 P
17 P
8
U
14
9 P
10 W
11 G
12 W
13 W
18 W
15 N
22 M
TM061 Rheem 27 Water Star Service Instructions – Issued: 11/10
REV A Issued 08/13
This document is stored and maintained electronically by
Normal Value
Wire
Colour
BL1 – BR4
216~264 VAC
W1 – W2 50kΩ – 500kΩ
2 – 5 VDC (pulse)
BR1 – BK2
>1310 pulses/minute
R3 – BK2 11 – 17 VDC
BL4 – W6 144 – 192 VDC
R3 – BL4
12 - 18 VDC
4 – 10 VDC (Pulse)
Y1 – BL4
>4800 pulses/minute
W6 – BK3
Refer to thermistor
Y5 – BK3
resistance chart on following
R4 – BK3
page.
BL7 – BK3
0.3 – 100VAC
W1 – GND
1 – 100VAC
1.5 – 14 VDC
R1 – BK2
40 – 80Ω
75 – 100 VDC
Y1 – BK8
0.8 – 2.4kΩ
R1 – R4
90 - 110VAC
75 – 100VDC
W2 – BK8
0.8 – 2.4kΩ
75 – 100VDC
R5 – BK8
0.8 – 2.4kΩ
75 – 100VDC
BL6 – BK8
0.8 – 2.4kΩ
W2 – BK8 8 – 16VDC
R7 – BK8 8 – 16VDC
Less than 1VDC (Limiter on)
GR6 – BK8
4 – 6VDC (Limiter Off)
W2 – BK8 8 – 16VDC
R7 – BK8 8 – 16VDC
Less than 1VDC (Limiter on)
GR6 – BK8
4 – 6VDC (Limiter Off)
Service. All printed copies not bearing this statement in RED are deemed "uncontrolled"
Point to Check
Main Power.
Over Heat Limiter.
Water Flow Sensor pulse signal.
(Only when water is flowing)
Water Flow Sensor.
Fan Motor has proper voltage.
Fan Motor has proper voltage.
Fan Motor producing a regular pulse.
Cold water inlet thermistor.
Heat exchanger thermistor.
Hot water outlet thermistor.
Ambient air thermistor.
Flame rod not detecting flame.
Flame rod detecting flame.
PGFR (Proportional Gas Flow
Regulating Valve)
GISV 0 (Gas Inlet Solenoid Valve 0)
(Primary fuel inlet to gas valve)
Igniter
Solenoid valve (SV1)
(Fuel to ODS and front right burner)
Solenoid valve (SV2)
(Fuel to back right burner)
Solenoid valve (SV3)
(Fuel to left side burner)
Water volume control motor has
proper voltage.
Water volume control motor has
proper voltage.
Water volume control motor position
switch is normal.
Water bypass control motor has
proper voltage.
Water bypass control motor has
proper voltage.
Water bypass control motor position
switch is normal.
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