E13
CTC Exhaust Over-Temperature / Flue Sensor Fault

Display shows E13 and unit locks out; may occur after long operation

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Failed flue gas temperature sensor, Blocked exhaust vent, Incorrect venting materials, Overfiring due to gas valve fault

How to Fix / Troubleshooting

Safety first: Turn off power and gas. Hot flue components can cause burns; allow them to cool.

Steps to check:

  • Inspect the exhaust vent for proper slope, length, and material per CTC installation instructions. Correct any obvious installation issues.
  • Check for obstructions or crushed sections in the vent pipe.
  • Locate the flue gas temperature sensor on the exhaust manifold. Inspect wiring and reseat the connector.
  • Test the flue sensor resistance and compare to specifications. Replace the flue temperature sensor if out of range.
  • If venting and sensor are good, the unit may be overfiring due to a faulty gas valve assembly or control board; this requires a professional combustion analysis and repair.
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Repair Difficulty

Professional Required 5/5

Required Part

Flue Temperature Sensor
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