Gibson
Marginal Venting or Combustion Air Problem
Furnace cycles off on very cold days but runs normally in mild weather
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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
Frost or ice buildup on PVC vent termination, Undersized combustion air openings, Long horizontal vent runs on Gibson condensing furnace, Pressure switch near trip point
How to Fix / Troubleshooting
Safety first: Use caution when working outside in icy conditions or on ladders.
Steps to check:
- Inspect vent termination: On very cold days, check for frost or ice blocking the exhaust or intake pipes. Carefully remove any buildup.
- Combustion air: Ensure any combustion air grilles or louvers to the furnace room are open and unobstructed.
- Professional check: A technician can verify vent sizing and pressure switch operation and may adjust or reroute venting if needed.
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Repair Difficulty
Medium
3/5
Required Part
Vent Pipe Assembly
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