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Help – My Furnace Vents Are Blowing Cool Air!

Furnace technician

If you’re feeling cool air blowing through your vents, it could be a simple furnace fix – or a complicated furnace repair.

Here are three common causes for cool air coming from your furnace vents that you can fix yourself.

  1. Your thermostat is set to ON rather than AUTO – If your furnace is switching between blowing warm and cool air, but the blower is constantly running, the problem could be your thermostat. If your thermostat’s fan setting is set to ON, the blower will run even when your furnace isn’t warming the air.

    Try setting your thermostat fan to “AUTO” rather than “ON” and see if it takes care of the problem.

  2. Your furnace has overheated – If your vents are blowing cool air or no air at all after consistently blowing warm air, the furnace could be overheated. A furnace has a “limit switch” that turns the furnace burner off as a safety measure; the blower remains on for a while to cool the burner, then shuts off.

    A common cause for furnace overheating is a dirty furnace air filter, which blocks airflow and forces your furnace to overwork to do its job.

    Give your furnace a time out and try switching the air filter. But keep a close eye on your heating system – repeated overheating can damage the furnace’s heat exchanger, which is expensive to fix and may even damage your equipment permanently!

  3. Your pilot light is out – If your gas furnace is only blowing cold air, your pilot light may be out.

    If you’re comfortable with doing so, re-ignite your pilot light, following the manufacturer’s instructions carefully. If you’re not, don’t worry – just contact us. If the pilot won’t light, make sure the furnace’s gas valve switch is in the “on” position (parallel/in line with the gas supply pipe). If the pilot lights but won’t stay lit, your thermocouple (the copper rod you see contacting the pilot flame) needs service or replacement – a job for professional heating system technician.

Still having problems? Contact us today and we’ll straighten out the problem. Or better yet, sign up for one of our high-value Service Plans so you can avoid these problems in the future. Do it before November 30 and it will cost you less than a tune-up! Contact us to learn more.