Ruud
No Heat Call or Open Safety Circuit
Furnace fan runs but burners never ignite; cool air blows from vents.
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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, Open high limit or rollout switch, Disconnected W wire at control board, Faulty control board heat relay
How to Fix / Troubleshooting
Safety: Turn off power before checking wiring or safety switches.
Steps to check:
- Thermostat mode: Confirm thermostat is in HEAT mode and set above room temperature.
- Check W terminal: Ensure the W wire is securely connected at the furnace control board.
- Inspect safety switches: Locate high limit and rollout switches and check for loose wires. Some rollout switches have manual reset buttons; if tripped, press once. If they trip again, call a technician.
- Observe LED codes: Look for any diagnostic flashes indicating which safety is open.
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Repair Difficulty
Medium
3/5
Required Part
High Limit Switch
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