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Troubleshooting a Home Furnace and Air Conditioning Thermostat


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PROBLEM: Furnace Produces No Heat

Furnace Produces No Heat

Possible Causes

Possible Repairs

  • Reset circuit breaker or replace fuse.
  • Remove thermostat cover and gently clean components especially the bimetallic coil and the switch contact surfaces if the thermostat does not have a mercury switch.
  • Set the thermostat to its lowest setting and clean the bimetallic coil with a soft brush or compressed air. Set the thermostat to its highest setting and clean the coil again. Reset the thermostat to its desired setting.
  • Tighten any loose screw terminals. If a wire is loose from its terminal, place wire back on terminal clamp and tighten screw.
  • Check for loose connection or disconnected wire on low-voltage transformer usually mounted on furnace
  • On electronic models, check to see if the display is working indicating power. If it is not working, replace the batteries in the electronic thermostat.

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