A.O. Smith GTS-305-NE Service Manual page 11

Code Fault
02 No burner operation during
freeze protection mode
10 Air Supply or Exhaust
Blockage
11 No Ignition
12 Flame Failure
On-Demand Gas Tankless Water Heater Service Manual
Fault Isolation
Remedy
Service Call - Check for possible freeze damage to heat exchanger.
Ensure approved venting materials are being used.
Check that nothing is blocking the flue inlet or exhaust.
Check all vent components for proper connections.
Ensure vent length is within limits.
Ensure condensation collar was installed correctly.
Verify dip switches are set properly.
Check fan for blockage.
Check that the gas is turned on at the water heater, gas meter, or cylinder.
Ensure gas type and pressure is correct.
Ensure gas line, meter, and/or regulator is sized properly.
Bleed all air from gas lines.
Verify dip switches are set properly.
Ensure appliance is properly grounded.
Disconnect 2-Unit or Multi-Unit connections to isolate the problem.
Ensure igniter is operational.
Check igniter wiring harness for damage.
Check gas solenoid valves for open or short circuits.
Remove burner cover and ensure all burners are properly seated.
Remove burner plate and inspect burner surface for condensation or debris.
Check that the gas is turned on at the water heater and gas meter. Check for
obstructions in the flue outlet.
Ensure gas line, meter, and/or regulator is sized properly.
Ensure gas type and pressure is correct.
Bleed all air from gas lines.
Ensure proper venting material was installed.
Ensure condensation collar was installed properly.
Ensure vent length is within limits.
Verify dip switches are set properly.
Ensure appliance is properly grounded.
Disconnect keypad.
Disconnect all 2-Unit or Multi-Unit connections to isolate the problem.
Check power supply for loose connections.
Check power supply for proper voltage and voltage drops.
Ensure flame rod wire is connected.
Remove flame rod and check for carbon build-up; clean with sand paper or emery
cloth.
Disconnect and reconnect all wiring harnesses on unit and PC board.
Check all components for electrical short.
Check gas solenoid valves for open or short circuits.
Remove burner plate and inspect burner surface for condensation or debris.
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