Rinnai RHFE-551FA Service Manual page 24

Troubleshooting
(BL) Combustion Motor:
NOTE: If your meter does not have a hertz scale, please
refer to voltage and resistance readings listed
below. If you have a hertz scale, check the
following items first. Hertz reading across black -
white wires, pins 41 and 42.
Voltage and resistance check for (BL).
WIRE COLOR
Red - Yellow
Black - White
(FM) Convection fan motor:
WIRE COLOR
Red - Gray
(TH) Thermistor:
Check the thermistor by inserting meter leads into each end of the thermistor plug. Set your meter to the 200k
scale and read resistance. You should be able to apply heat to the thermistor bulb and see the resistance
decrease. Then apply ice to the thermistor bulb and the resistance should increase.
EXAMPLES: 41 °F = 91 k ohms
50 °F = 65 k ohms
68 °F = 39 k ohms
86 °F = 23 k ohms
(FR) Flame Rod:
Flame rod - yellow wire = pin #27. Low fire current should be 1.3 to 2.0 micro amps (Fa). High fire current should
be 4 to 8 micro amps, depending on gas type being used.
NOTE: Improperly setup and/or converted units can soot and cause carbon to accumulate on flame rods. This
will cause hard lockouts. If carbon is found on the flame rod, remove and clean carbon from rod. Then
you will need to confirm manifold gas pressure, proper air dampers and ensure vent is clear. Also, check
for proper orifices.
24
VOLTAGE
1-2 VDC low fire to 7.6
-18 VDC high fire
N/A
VOLTAGE
80-94 VAC low fire to
95-104 VAC high fire
Rinnai Direct Vent Service Manual
RHFE-431 - LP UNITS
Lo fire - 44 Hz.
Hi fire - 81 Hz.
RHFE-431 NG UNITS
Lo fire - 44 Hz.
Hi fire - 81 Hz.
RESISTANCE
1.2 - 1.8 mega ohms
9.4 k - 9.9 k ohms
RESISTANCE
90-180 ohms
RHFE-431FA Series
RHFE-556FA/FTRA Series
RHFE-556 LP UNITS
Lo fire - 47 Hz.
Hi fire - 106 Hz.
RHFE-556 NG UNITS
Lo fire - 48 Hz.
Hi fire - 106 Hz.
PIN NO.
39 - 40
41 - 42
PIN NO.
21 - 22