Start with the free one: if your thermostat fan is set to ON instead of AUTO, the blower runs between heating cycles and pushes room-temperature air that feels cold. Flip it to AUTO and see if the 'problem' disappears.
Next in line: a clogged filter overheating the furnace and tripping its safety limit, a pilot or ignition failure, or a condensate blockage on high-efficiency units. All three shut real heat down while the fan keeps blowing.
If the basics check out and it's still blowing cold, stop cycling the power and call — repeated restart attempts on an ignition fault just wear parts. We troubleshoot on the phone first, and no-heat calls get same-day priority.
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Questions about your own system?
Ask Roy in the corner, call us, or book a free assessment — whichever suits you.