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2. Check the resistance of the flow
adjustment valve. To check it,
2.1
Turn off electrical power to the
water heater, then.
2.2
Unplug the fl ow adjustment
valve's connector from the
computer board. (See Wiring
Diagram on page 28.)
2.3
Check the resistance between
the red and black wires.
Normal resistance (black-red):
90 to 200 Ω. If the resistance is
out of range, replace the fl ow
adjustment valve.
3. Check the voltage of the flow
adjustment valve where its connector
plugs into the PCB. Measure between
the black and red wires. (See page 20
or 20.) Normal voltage range (black-
red):
7 VDC - 16 VDC. If the voltage is out
of range, replace the computer board.
(See page 28.)
Code 661: Bypass valve fault
This code indicates a bypass valve fault.
1. Inspect the bypass valve (item number
403) for the following:
•
Broken or disconnected wires
(Be sure to look behind the fuse box
and check the wire assembly from
the bypass valve. Wire colors: red,
yellow, white, blue, brown.)
•
Locked motor drive due to debris
or scale build up inside the valve
assembly
•
Water leakage at the bypass valve
2. Check the resistance of the bypass
valve. To check it,
2.1
Turn off electrical power to the
water heater, then.
2.2
Unplug the bypass valve's
harness. There is a connector in
the middle of the harness which
you can access by removing
the computer board. The
harness' wire colors are red,
yellow, white, blue, brown). See
connector #715 on page 73.
2.3
Check the resistance between
the brown and red wires. (You
can use the pins in the female
connector.) Normal resistance
(brown-red): 50 to 85 Ω. If
the resistance is out of range,
replace the bypass valve.
3. Check the voltage of the bypass valve.
To check it, measure between the
brown and red wires. (Connector #715
on page 73.) Normal voltage range
(brown-red):
3 VDC - 11 VDC. If the voltage is out
of range, replace the computer board.
(See page 73.)
Code 701: Computer Board
Fault
This code indicates a computer board or
outlet thermistor fault.
1. Inspect the computer board (PCB)
for connection/breakage of wires
and/or burn marks.
2. Check the operation of the outlet
thermistor as follows:
2.1
Push the on/off bu on on
the temperature controller
or remote controller so the
orange STAND BY LED turns
off .
2.2
Run water through the
heater.
2.3
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
On-Demand Water Heater Service Handbook for X3P Models
thermistor. The readings
should be similar and it
should be reading the
temperature of the supply
water. If there is a diff erence
of more than fi ve degrees,
refer to Code 311, 321, 331,
341 or 351: Thermistor
Failure, p. 18.
When you are finished,
retest the water heater.
Code 711: High Limit Switch /
Overheat Cutoff Fuse Circuit is
Compromised
When power is turned on to the
heater, the computer performs a
diagnostic check of 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 main gas valve
located next to the PCB and the gas
solenoid valve assembly located
above the heat exchangers. (For
each connector, the number
stamped on the metal must match
the number that is printed on the
wire's label. See page 28)
3. Check the High Limit switch. Refer
to "Code 111 or 121: Ignition
Failure / Flame Loss," See on page
16.
4. The Overheat Cutoff switch may be
compromised. Refer to "Checking
the Overheat Cutoff Fuse (OHCF),"
page 32.
5. There may be a computer board
(PCB) and/or gas valve fault. Refer
error codes 510 and 551.
•
21
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