50
F00
High temperature switch limit
exceeded 194
o
F.
1. Try reset. If F00 repeats, create a demand for hot water. (DANGER: Use caution to
prevent burn injury.) If water is above 194
o
F, test upper and lower temperature sensor
with an ohmmeter. (Refer to resistance chart, this section.) Replace bad sensor. If water
is below 194
o
F, test high temperature switch and wiring with ohmmeter. Switch should be
closed at this point. If not, replace switch.
2. If unit did reset successfully, let the heater run and go into the status menu to check the
upper and lower temperature sensor. If either reading displayed does not make sense,
check appropriate sensor with ohmmeter. (Refer to resistance chart, this section.)
Replace bad sensor. Do an OHMs reading on both sensors to check continuity.
F01
Vent temperature limit
exceeded.
1. Inspect all flue piping. If the flue is damaged or shows signs of overheating, repair or
replace the flue parts as necessary before proceeding.
2. If the flue piping system is intact, not damaged and there is no sign of the flue
overheating (such as discoloration or melting), push the red reset button on the flue
switch
3. Be sure the heater is connected to a water supply and full of water.
4. Push the RESET button on the heater control panel. The appliance should light. If the
appliance lights, proceed to step 5. If the appliance does not light and the display again
begins to flash F01, inspect the wiring to the flue switch, repairing or replacing as
necessary. If the wiring is intact, replace the flue switch, using care to mount the new flue
switch in the same position and mounting holes as the old one. If the display flashes a
code other than F01, follow the troubleshooting guide for that code.
5. Observe operation for 5 minutes. Place the probe of an exhaust analyzer into the flue
system within 6 feet of the heater. The exhaust temperature should not rise above 190
o
F
after several minutes of operation.
6. If the flue temperature is below 190
o
F and the heater again goes into lockout displaying
F01, replace the flue switch, using care to mount the new flue switch in the same position
and mounting holes as the old one. If the display flashes a code other than F01, follow the
troubleshooting guide for that code.
7. If the flue temperature increases to over 190
o
F, consult HTP for further assistance.
F02
Interrupted or shorted upper
temperature sensor.
1. Check the electrical connection to the appropriate temperature sensor.
2. If connection is okay, replace bad sensor.
F03
Interrupted or shorted lower
temperature sensor.
F05
Upper temperature sensor
o
1. If water in tank is not greater than 194
F, check wiring. Repair if faulty.
2. If wiring is okay, check appropriate sensor with ohmmeter and compare to reading in
resistance chart above. If reading does not agree with water temperature, replace bad
sensor.
F06
Lower temperature sensor
exceeds 194
o
F.
F09
No flame detected – Heater
will make three attempts at
ignition before the control
goes into this lockout
condition. Will reset in 1 hour.
1. Watch the igniter through the observation window provided.
2. If there is no spark, check the spark electrode for the proper ¼” gap.
3. Remove any corrosion from the spark electrode and flame rectifier probe.
4. If there is a spark but no flame, check the gas supply to the heater.
5. If there is a flame, check the flame sensor.
6. Check any flue blockage or condensate blocks.
F10
Loss of flame signal – The
heater will relight 4 times
before the control goes into
this lockout condition. Will
reset in 1 hour.
1. Monitor the gas pressure to the unit while in operation.
2. Assure that the flame is stable when lit.
3. Check to see if the green light on the display module is out while the heater is running.
4. If the green light doesn’t come on or goes off during operation check the flame signal
on the status menu.
5. If the signal reads less than 1 microampere, clean the flame rectifier probe.
6. If the flame rectifier probe continues to read low, replace it.
F11F
False flame signal – The
heater will lock out if it senses
a flame signal when there
should be none present.
1. Turn the gas off to the unit at the service valve.
2. If the flame signal is still present replace the igniter.
3. If the flame signal is not present after turning off the gas supply, check the gas valve
electrical connection.
4. If there is no power to the gas valve, remove the valve and check for obstruction in the
valve seat or replace the gas valve.
5. Turn the gas on at the service valve after corrective action is taken.
F13
incorrect – The heater will
lock out if it senses that the
fan speed is less than 70% of
expected rate for more than
1. Check the combustion air fan wiring.
2. Replace the combustion air fan.
3. Replace the control board.
Table 13 NOTE: If you replace a part to remedy a fault, it is recommended that you cycle the unit at least
three or four times to assure the fault has been resolved.
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