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Safe checks before scheduling service
- Set the thermostat to HEAT and raise the setpoint above room temperature.
- Check the filter for severe restriction.
- Confirm accessible furnace switches and breakers are on.
- Look for a visible fault code through the furnace sight window if one is provided; do not remove panels to search for one.
- Make sure supply and return vents are not blocked.
If you encounter exposed wiring, smoke, a gas odor, a carbon-monoxide alarm, or another immediate safety concern, stop troubleshooting and follow the appropriate emergency guidance.