16 • Condensing Models: On-Demand Water Heater Service Handbook
TR
OUBLE
SHOO
TING
Propor onal Gas Valve /
Computer Board Fault
Error Code: 701
1. Verify that the red/white
harness is connected at both the
proportional valve solenoid and
the computer board (PCB).
2. Inspect the computer board (PCB)
for connection/breakage of wires
and/or burn marks.
3. Check the operation of the outlet
thermistor as follows:
3.1
Push the on/o
ff
bu on on
the temperature/remote
controller so the STAND BY
LED turns o
ff
.
3.2
Run water through the
heater.
3.3
Check the reading of
the outlet thermistor by
pushing the INFO bu on on
the temperature/remote
controller two mes.
Compare it to the inlet
thermistor. The readings
should be similar and it
should be reading the
temperature of the supply
water. If there is a di
ff
erence
of more than
fi
ve degrees,
go to Error Code 311, then
retest the heater.
4. Check the proportional gas valve
as described in the following sub-
steps. The proportional valve is
located at the bottom of the gas
valve assembly and has red and
white wires connected to it.
4.1 Turn
o
ff
the power supply.
4.2
Check all wire connec ons
and make sure that they are
secure and free of burns or
cuts.
5. Verify that supply gas pressure is
within specifications.
6. Check the resistance across the
proportional valve (red, white
wires). Normal value is 20-40
Ω
. If
the resistance is outside this range,
replace the gas valve. NG part
320273-356, LP part 320273-354.
High Limit Switch / Overheat
Cuto
ff
Fuse Circuit is
Compromised
Error Code: 711
When power is turned on to
the heater, the computer takes
approximately 20 seconds to boot
up. During this time, the computer is
checking the gas valve, high limit, and
Overheat Cutoff Fuse (OHCF) circuits.
If any of these are compromised, this
code will appear.
1. Inspect the dark blue common
wire to the high limit switch, the
OHCF, and the gas valves for any
breaks or cuts.
2. Verify proper wiring harness
connections to the gas valve
solenoids. (For each connector,
the number stamped on the metal
must match the number that is
printed on the wire’s label. See
Figure 7, page 14.)
3. Check the High Limit switch. Refer
to “Ignition Failure / Flame Loss”
on page 12.
4. The Overheat Cutoff switch may be
compromised. Refer to “Checking
the Overheat Cutoff Fuse (OHCF)”
on page 27.
5. There may be a computer board
(PCB) and/or gas valve fault. Refer
to error codes 510 and 551.
False Flame Detec on
Error Code: 721
1.
WARNING! Shut off all gas and
power to the unit.
The problem
could be the flame sensor, but if it
isn’t, this is a very dangerous
situation.
2. Inspect the flame sensor. Clean
it if necessary. See “Cleaning the
Rod Assembly (Flame Sensor and
Air/ Fuel Ratio Rod)” on page
28.
3. Contact the technical service
department for further assistance.
Remote Control Problem
Error Code: 741
This error code only occurs when
there is a miscommunication between
the temperature remote controller
and water heater. This code is not for
the built in controller on the indoor
models. (Remote controllers for
outdoor models will vary in the field.
Prior to April 2015, outdoor models
were equipped with remote controller
TM-RE40/9008172005; current
outdoor models are equipped with
TM-RE42/9009069005.)
1. Make sure that all wiring is
connected to the remote
controller properly.
2. Verify that only a single remote
is installed. With indoor models,
only one remote may be used
in addition to the built-in
temperature controller.
An incorrect remote or multiple
remotes will result in this error
code. If an incorrect remote is
installed, a 741 or 74 code will
appear.
If you disconnect the remote from
the heater with the power supply
