Bosch
No Heat / Burner Not Firing
Furnace runs but does not produce heat; blower or pump operates but burner never ignites
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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
Thermostat not calling for heat or miswired, Gas supply shut off, Faulty gas valve, Ignition control lockout not reset
How to Fix / Troubleshooting
Safety: If you smell gas, do not attempt to light the furnace. Evacuate and call your gas supplier.
- Thermostat: Confirm the room thermostat or Bosch controller is set to HEAT and above room temperature. Replace batteries if applicable.
- Gas valve: Ensure the manual gas shutoff near the furnace is parallel to the pipe (open). Check that other gas appliances work.
- Reset lockout: Many Bosch furnaces have a reset button on the control or burner. Press and hold as specified in the manual to clear lockout. If the unit repeatedly locks out, stop resetting and investigate further.
Gas valve and ignition control testing should be left to a licensed technician.
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Repair Difficulty
Medium
3/5
Required Part
Gas Valve Assembly
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