Rinnai RH180 Installation Fundamentals page 56

Maintenance Codes
Code Definition
38 CO or FV sensor.
52 Modulating
solenoid valve
signal.
61 Combustion fan.
63 Circulation flow
rate has dropped
below 1.3 gpm.
71 Solenoid valve
circuit fault (SV0,
SV1, SV2, SV3).
56
Remedy
Licensed
Check sensor wiring for damage.
professional
Measure resistance of sensor.
only
Replace sensor.
Licensed
Check modulating gas solenoid valve wiring harness for loose or damaged
professional
terminals.
only
Measure resistance of valve coil.
Licensed
Ensure fan will turn freely.
professional
Check wiring harness to motor for damage and/or loose connections.
only
Measure resistance to motor winding.
Check water filter for blockage.
Check pump operation and wiring.
Licensed
Clean heat exchanger.
professional
only
Licensed
Check wiring harness to all solenoids for damage and/or loose connections.
professional
Measure resistance of each solenoid valve coil.
only
Replace PCB.