Tempstar Low Heat Output

Furnace runs but delivers insufficient 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

Clogged filter or coil restricting airflow, Incorrect gas input rate to Tempstar furnace, Partially closed gas shutoff, Blower speed set too high for heating

How to Fix / Troubleshooting

Safety: Turn off power before adjusting blower wiring; gas adjustments should be done by a professional.

  • Step 1 – Check filter and coil: Replace the filter and inspect the Tempstar evaporator coil for dirt buildup. Have it cleaned if necessary.
  • Step 2 – Verify registers: Ensure all supply registers are open and not blocked.
  • Step 3 – Check blower speed: Refer to the Tempstar wiring diagram and confirm the correct speed tap is used for HEAT. If airflow is too high, the air may not heat adequately.
  • Step 4 – Professional gas check: Have a technician verify the furnace input rate (clocking the gas meter) and adjust the gas valve if needed.
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Repair Difficulty

Medium 3/5

Required Part

Tempstar Furnace Gas Valve
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