Thermia
No Power / Dead Furnace
Furnace does not start at all; no blower, no inducer, no display or LEDs.
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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
Tripped circuit breaker, Turned-off furnace service switch, Blown internal fuse on Thermia control board, Failed transformer or control board
How to Fix / Troubleshooting
Safety first: Before resetting breakers, ensure there is no burning smell or visible damage.
- 1. Check breaker: Locate the furnace breaker in the electrical panel and reset if tripped. If it trips again immediately, do not continue resetting—call a technician.
- 2. Verify service switch: Ensure the furnace disconnect or light switch near the Thermia furnace is in the ON position.
- 3. Inspect access door switch: Many Thermia furnaces have a door switch that cuts power when the panel is removed. Make sure the panel is properly installed and engaging the switch.
- 4. Check control board fuse: With power off, remove the access panel and inspect the low-voltage fuse on the control board. Replace only with the same rating after checking for shorts.
- 5. If still dead: The transformer or control board may have failed and should be tested and replaced by a professional.
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Repair Difficulty
Medium
3/5
Required Part
Main Control Board
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