Rheem 874W27NF, Service Manual, Page: 21 / 61

21
TM061 Rheem 27 Water Star Service Instructions
– Issued: 11/10
REV A Issued 08/13
This document is stored and maintained electronically by Service. Al
l printed copies not bearing this statement in RED are deemed “uncontrolled”
Diagnostic Points on Printed Circuit Board
Measurement Point
Normal Value Point to Check
No. Connection
Wire
Colour
1 A
BL1
– BR4 216~264 VAC
Main Power.
2 T W1
– W2
50k
Ω – 500kΩ
Over Heat Limiter.
3 S
BR1
– BK2
2
– 5 VDC (pulse)
>1310 pulses/minute
Water Flow Sensor pulse signal.
(Only when water is flowing)
R3
– BK2
11
– 17 VDC
Water Flow Sensor.
4 J
BL4
– W6
144
– 192 VDC
Fan Motor has proper voltage.
R3
– BL4
12 - 18 VDC Fan Motor has proper voltage.
Y1
– BL4
4
– 10 VDC (Pulse)
>4800 pulses/minute
Fan Motor producing a regular pulse.
5 P W6
– BK3
Refer to thermistor
resistance chart on following
page.
Cold water inlet thermistor.
6 P Y5
– BK3
Heat exchanger thermistor.
7 P R4
– BK3
Hot water outlet thermistor.
17 P BL7
– BK3
Ambient air thermistor.
8
U W1
– GND
0.3
– 100VAC
Flame rod not detecting flame.
14 1
– 100VAC
Flame rod detecting flame.
9 P R1
– BK2
1.5
– 14 VDC
PGFR (Proportional Gas Flow
Regulating Valve)
40
– 80Ω
10 W Y1
– BK8
75
– 100 VDC
GISV 0 (Gas Inlet Solenoid Valve 0)
(Primary fuel inlet to gas valve)
0.8
– 2.4kΩ
11 G R1
– R4
90 - 110VAC Igniter
12 W W2
– BK8
75
– 100VDC
Solenoid valve (SV1)
(Fuel to ODS and front right burner)
0.8
– 2.4kΩ
13 W R5
– BK8
75
– 100VDC
Solenoid valve (SV2)
(Fuel to back right burner)
0.8
– 2.4kΩ
18 W BL6
– BK8
75
– 100VDC
Solenoid valve (SV3)
(Fuel to left side burner)
0.8
– 2.4kΩ
15 N
W2
– BK8
8
– 16VDC
Water volume control motor has
proper voltage.
R7
– BK8
8
– 16VDC
Water volume control motor has
proper voltage.
GR6
– BK8
Less than 1VDC (Limiter on)
4
– 6VDC (Limiter Off)
Water volume control motor position
switch is normal.
22 M
W2
– BK8
8
– 16VDC
Water bypass control motor has
proper voltage.
R7
– BK8
8
– 16VDC
Water bypass control motor has
proper voltage.
GR6
– BK8
Less than 1VDC (Limiter on)
4
– 6VDC (Limiter Off)
Water bypass control motor position
switch is normal.