Electronic Control Display Troubleshooting - A.O. Smith 12 40GPC T 100 Service Handbook

ELECTRONIC CONTROL DISPLAY TROUBLESHOOTING

Please check guidelines below. For your safety, water heater service should be performed only by a qualified service person.
Read the
CONTROL DISPLAY STATUS
1. "POWER" Flashing
2. "HEATING" and "SHORT" Flashing
3. "HEATING" and "OPEN" Flashing
4. "HEATING", "OPEN", and "SHORT" Flashing
5. "ECO" and "OPEN" Flashing
ELECTRONIC CONTROL DISPLAY
GENERAL SAFETY INFORMATION
Communication Error
The system has detected a
communication error between the
upper and lower controls.
The self-diagnostic tests have
found a problem with an internal
circuit.
Ignition/flame failure.
The water heater has reached the
maximum number of retries and is
currently locked out for one hour.
Cycle the power to the water
heater off and on to reset.
Weak flame sensor current.
Water temperature in the tank has
exceeded 185°F (85°C) and has
activated the ECO.
supplied by the water heater manufacturer.
PROBLEM
1. Check the 5-conductor data cable that
2. Replace the upper control, if the error code
3. Replace the lower control if the problem persists.
1. Turn the power off for 10 to 20 seconds
2. If the error code persists or cannot be
1. Gas supply is turned off – pressure too
2. Low supply voltage – should be 115 –
3. Ensure flame sensor is making good
4. Ensure the flame sensor is clean – use
5. Ensure the hot surface ignitor is
6. Check for any cracks in the ignitor
7. Check resistance of the ignitor at room
1. Ensure flame sensor is making good
2. Ensure the flame sensor is clean – use
1. Turn the power off for 10 – 20 seconds
2. Replace the lower control if the error
20
SOLUTION
runs between the upper and lower
controls. Check that the wiring is not
broken, and the connectors on both ends
are properly seated in the mating
connectors.
does not clear - cycle power to the water
heater "Off" and "On" to reset.
then on again to clear the error code.
cleared, replace the lower control.
low. Ensure supply and manifold gas
pressures are within requirements in the
installation manual. Manifold gas
pressure is non-adjustable, if pressure is
off by more than 0.3" W.C. (75 Pa)
replace the lower control.
125 VAC.
contact with the burner flame, ensure
flame is steady.
ultra fine steel wool or Scotch-Brite
to clean the flame sensor.
positioned to provide consistent ignition.
assembly ceramic insulators – replace
ignitor assembly if damaged.
temperature (77°F – 25°C) at the plug
end. Replace ignitor if the resistance is
not within 1.72 to 2.4 ohms at room
temperature.
contact with the burner flame, ensure
flame is steady.
ultra fine steel wool or Scotch-Brite pad
to clean the flame sensor.
then on again to clear this error code.
code persists.
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pad
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