Guide: HVAC
Furnace not turning on? Check the simple things safely.
Check the thermostat is set to "heat" above room temperature, the furnace switch and breaker are on, the filter is not clogged, and the furnace panel door is closed properly. If it still will not start, shows an error code, or you smell gas, call an HVAC tech.
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Safe checks
- Thermostat. On "heat", set above the room temperature, fresh batteries.
- Power. A furnace has a switch that looks like a light switch on or near the unit, plus a breaker. Both need to be on.
- Filter. A blocked filter can make the furnace shut itself off to protect itself. The US Department of Energy advises cleaning or replacing furnace filters once a month or as recommended.
- Panel door. Many furnaces will not run if the front panel is not fully closed, because of a safety switch.
- Error light. Look through the small window on the panel. A blinking light often maps to a code on the inside of the door. Note it for the technician.
Smell gas, or a carbon monoxide alarm is going off? Get everyone outside and call your gas utility or 911 from there. The EPA lists leaking chimneys and furnaces, and back-drafting from furnaces and gas water heaters, among the sources of carbon monoxide in homes.
When it is a technician job.
Repeated short cycling, an igniter that clicks without lighting, a blower that runs with no heat, error codes that come back after a reset, or any gas smell. Do not keep resetting a furnace that locks itself out.
Questions
Common questions
Who do I call when my furnace will not turn on?
An HVAC technician. If you smell gas, leave the house first and call the gas utility.
Why does my furnace turn on and then shut off?
Common causes are a dirty filter, a dirty flame sensor, or the system overheating. If a new filter does not fix it, have it checked.
Being straight with you
We connect the call. We do not do the work.
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