No Heat? What to Do Right Now

First: if you smell gas or a carbon monoxide alarm goes off

If you smell gas (a rotten-egg smell), leave the house now. Don't flip light switches or use your phone inside. Call your gas utility's emergency line or 911 from outside.

If a carbon monoxide alarm sounds, get everyone, pets included, into fresh air and call 911. Don't go back in until responders say it's safe. Then call us so we can find the cause. See Carbon monoxide and your furnace.

1. Five-minute checks

These are safe for anyone and fix a surprising number of no-heat calls:

• Thermostat: set it to Heat, a few degrees above the room temperature, with the fan on Auto. If the screen is blank, replace the batteries if it uses them.
• Breakers: look for a tripped breaker labeled furnace, air handler, heat pump or HVAC. Reset it once. If it trips again, leave it off and call.
• Furnace switch: there's usually a light-style switch on or near the furnace. It has to be on, and it's easy to flip off by mistake.
• Filter: a badly clogged filter can make a furnace overheat and shut off. Replace it if you can't see light through it.
• Furnace door: the blower door has to be fully closed, or a safety switch keeps the furnace from running.
• Outdoor vents: on a high-efficiency furnace, make sure the white plastic vent pipes outside aren't blocked by snow, ice or leaves.

If those don't bring the heat back

For more detail by system type, see Furnace not heating or Heat pump not heating. Don't keep resetting a furnace that locks out. A system that shuts itself off is usually protecting itself from a real problem.

2. Keep the house warm safely while you wait

• Close blinds and curtains, and close doors to rooms you aren't using. Gather everyone in one or two rooms.
• Use electric space heaters only with at least three feet of clear space around them, plugged straight into a wall outlet, not a power strip or extension cord. Turn them off when you leave the room or go to bed.
• Never use a gas oven, stove or grill to heat the house. They can fill it with carbon monoxide.
• If you run a generator, keep it outdoors, at least 20 feet from windows, doors and vents. Never run one in the house or garage, even with the door open.
• Layer up and add blankets, especially for babies, older family members and anyone who is sick.

3. Protect your pipes

Frozen pipes are most likely when it drops below about 20 degrees outside, so these steps matter most on the coldest nights:

• Let faucets on outside walls drip. Moving water is less likely to freeze.
• Open the cabinet doors under kitchen and bathroom sinks on outside walls so warm room air can reach the pipes.
• Keep the garage door closed if water lines run through the garage.
• If a pipe has already frozen, open the faucet and warm the pipe gently with a hair dryer or warm towels. Never use an open flame.
• If a pipe has burst, shut off the main water valve and call a plumber.

4. What to tell us when you call

A few details help us show up with the right parts:

• What kind of system you have (gas furnace, electric furnace or heat pump), if you know.
• What it's doing: nothing at all, blowing cold air, starting and stopping, or making a new noise.
• Any blinking light or code on the furnace control board. You can often see it through a small window in the furnace door.
• How long it's been out, and whether anyone at home is especially vulnerable to the cold.

How HVAC Doctor can help

Call or text (859) 684-3259. One of the owners, Ahmad or Ammar, answers 24/7, and nights, weekends and holidays cost the same as a weekday. Mention our online special and the diagnostic is $39 (regularly $79), credited to the repair if you go ahead, and you get a firm price before any work starts. Most Lexington calls are same-day.

Common questions