No Heat in a Minnesota Winter: What to Check Before You Call

When the heat quits, start at the thermostat and work toward the furnace: the settings and batteries, the breaker, the furnace switch, the filter, the lower door, then the vent pipes and the condensate drain. Each check takes a minute or two, and any one of them can bring the heat back without a service call. If none of them does, you'll have the blink code and the details a technician needs, plus a plan for keeping the house and the pipes safe until help arrives.

Check these in order

1. Thermostat. Mode on Heat, not Cool or Off, and the setpoint a few degrees above the room temperature so the furnace gets a real call. A blank or dim screen usually means dead batteries. On a smart thermostat, look for a schedule, an away mode or an app setting holding the temperature down. A blank screen on a thermostat with no batteries can mean the furnace itself has lost power, which the next three checks cover.
2. Breaker. Find the furnace breaker in the electrical panel. If it's tripped, reset it once. If it trips again, leave it off and call. That's a short or a failing part, and a second reset won't change it.
3. Furnace switch. It looks like a light switch, mounted on the side of the furnace, on a nearby joist or wall, or at the top of the basement stairs. It gets bumped off by someone carrying laundry or storage boxes. Make sure it's on.
4. Filter. Pull it out and look. A filter packed with dust starves the furnace of air until it overheats, and a limit switch shuts the burners off to protect it. Put in a new one with the arrow pointing toward the furnace.
5. Lower door. The blower door presses a safety switch. If the door is off or sitting crooked, the furnace has no power. Push it firmly into place. Never tape or hold that switch in to run the furnace with the door off.
6. Vent pipes outside. A high-efficiency furnace vents through two white PVC pipes out a side wall or the roof. Drifted snow or a frost ring at the opening will keep it from lighting. Clear snow by hand, gently, because cold PVC cracks; our guide to clearing a frozen furnace vent has the steps. If the pipes come out through the roof, stay off the roof and call.
7. Condensate drain. Those same furnaces make water. Follow the small drain hose from the furnace to the floor drain or to a condensate pump, and make sure the pump is plugged in and isn't full. A drain that runs through a cold garage, a crawlspace or out a wall can freeze and shut the furnace down; see frozen condensate lines.
8. Fuel. On propane, check the tank gauge. If it's empty, call your supplier; they normally leak-check the system before the gas goes back on. On natural gas, if the gas stove won't light either, call the gas utility. If the handle on the furnace's gas line sits crosswise to the pipe, the gas to the furnace is off. Don't turn it on yourself. Someone may have shut it for a reason, so call a technician.

What does the blinking light on a furnace mean?

Most modern furnaces have a control board with a small status light, visible through a window in the lower door. A steady glow or a slow, even blink usually just means the board has power. A fault shows up as a count: a set number of flashes, a pause, then the same count again. Some brands flash a two-part code with a pause between the parts, so count both.

Count it before you touch anything, or take a short video with your phone. Taking the lower door off cuts power, and on many furnaces that clears the code. Then match the count to the chart printed inside the door or in the owner's manual. The wording differs by brand, but most charts include these faults:

Then reset once. Turn the furnace switch off for about 30 seconds, turn it back on, and raise the thermostat. If the furnace starts and runs a full cycle, you have heat for now, but mention the code at your next tune-up. If it locks out again, leave it off. Repeated resets hide the fault, and a furnace tripping a safety switch shouldn't keep firing. Our furnace won't ignite guide walks through the startup sequence if you want to see exactly where yours stops.

How fast does a house cool down with no heat?

A tight newer house holds its heat for a good while. Older Minneapolis and Saint Paul houses cool faster. Plenty of pre-1940 houses went up without wall insulation, and enclosed front porches, kitchen sinks on outside walls and bathrooms over unheated space are where pipes freeze first.

• Open the cabinet doors under sinks on outside walls so room air reaches the pipes.
• Let a slow drip run from faucets on outside walls. Moving water is slower to freeze.
• Keep interior doors open to the kitchen, bathrooms and laundry so what heat you have reaches the plumbing, and keep the garage door shut if water lines run through the garage.
• Find the main water shutoff now, usually where the water line enters the basement, so you can close it fast if a pipe splits.
• If a faucet slows to a trickle or stops, a pipe may be frozen. Leave that faucet open, and never thaw a pipe with an open flame.

Space heaters are fine used carefully: one in good condition, plugged straight into a wall outlet instead of an extension cord, with 3 feet of clear space from bedding, curtains and furniture, and turned off when you leave the room or go to sleep. Never heat the house with a gas oven, a grill, a camp stove or a generator. They put out carbon monoxide. Minnesota law requires working CO alarms within 10 feet of every sleeping room, and our CO alarm placement guide shows where they go.

Two setups have their own stopgaps. If you heat with a boiler and radiators, as many older Saint Paul houses do, the cast iron holds warmth for a while after the boiler stops. Leave the pressure, the water feed and the relief valve to a technician. If you have a heat pump and the heat pump is the part that quit, the Emergency Heat setting on the thermostat runs your backup heat by itself, whether that's a furnace or electric heat strips.

When should you stop checking the furnace and call?

Call right away, without more resets, if:

• The breaker trips a second time.
• The furnace locks out again after one reset.
• You smell something burning, electrical or like exhaust.
• The chart points to flame rollout, or you see scorch marks near the burners.
• Water is pooling under the furnace or dripping onto the wiring.
• The blocked vent comes out through the roof.

When you call, tell us the blink count and what the furnace does when it tries to start: nothing at all, the inducer runs with no glow, the igniter glows with no flame, or it lights and then drops out. Add whether you have natural gas or propane, and the brand and rough age of the furnace if you know them. That helps the technician arrive with the likely parts on the truck.

Getting a technician out

We're open 7 days, 7am–9pm, and no-heat calls go to the front of the schedule. Call 612-429-3465. A furnace repair visit carries a $79 trip charge, waived when you approve the repair, and you get a written, flat-rate price before any work starts. We work across both cities and the towns around them at the same pricing; see furnace repair in Minneapolis and furnace repair in Saint Paul.

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