Armstrong Air
Underfiring or Low Heat Output
Furnace runs but does not produce enough heat; home feels cool even though furnace cycles normally.
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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
Low gas pressure to Armstrong Air furnace, Incorrect orifice size, Partially plugged burners, Oversized duct system or high heat loss
How to Fix / Troubleshooting
Safety: Gas pressure and combustion adjustments must be performed by a licensed HVAC technician.
Homeowner checks:
- Filter and airflow: Ensure a clean filter is installed and all registers are open. Poor airflow can reduce perceived heat.
- Thermostat settings: Verify the thermostat is not set to an energy-saving program that lowers temperature unexpectedly.
Technician checks:
- Measure inlet and manifold gas pressures and adjust the Armstrong Air gas valve regulator as needed.
- Verify correct burner orifices for the fuel type (natural gas vs LP) and altitude.
- Clean burners and check for proper flame pattern.
- Confirm furnace size and duct design are appropriate for the home.
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Repair Difficulty
Hard
4/5
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