Tappan
Low Heat Output / Underfiring
Furnace runs but does not produce enough heat; home never reaches set temperature.
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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
Incorrect gas input to Tappan gas valve, partially clogged burners, restricted return air, thermostat calibration off
How to Fix / Troubleshooting
Safety: Gas input and combustion adjustments should be performed by a licensed technician. Homeowners can safely check airflow and thermostat settings.
Steps (homeowner level):
- Verify the thermostat is set to HEAT and not in setback mode. Replace batteries if applicable.
- Replace the furnace filter and ensure all supply and return vents are open.
- Observe the burners through the sight glass. Flames should be mostly blue and steady. Yellow, lazy flames or uneven burner ignition indicate a need for professional cleaning and adjustment.
- If the furnace cycles on and off frequently without reaching temperature, have a technician check temperature rise, gas input, and duct sizing.
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Repair Difficulty
Hard
4/5
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