E20
CTC
Safety Sensor Wiring Open/Short
Furnace indicates low flame rollout or vent temperature sensor wiring fault.
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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
Broken wire to rollout or limit switch, Shorted sensor wiring to cabinet, Loose spade connectors on safety string, Incorrectly wired replacement switch
How to Fix / Troubleshooting
Safety first: Turn off power and gas. Do not operate the furnace with safety circuits bypassed.
Steps:
- Follow the low-voltage safety circuit wiring from the CTC control board to each rollout, limit, and vent temperature switch.
- Inspect for broken, pinched, or burned wires and loose push-on connectors.
- Repair or replace damaged wiring using the same gauge and temperature rating, and crimp new insulated terminals as needed.
- Verify that any recently replaced switches are wired to the correct terminals and not accidentally grounded.
- After repairs, restore power and test operation.
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Repair Difficulty
Medium
3/5
Required Part
CTC Safety Circuit Wiring Harness
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