What to Do When Your Furnace Stops Working in Winter

Quick Answer: First Steps When Your Furnace Stops

If your furnace quits in winter, immediately check the thermostat (set to heat, temperature above room, fresh batteries), confirm the circuit breaker hasn’t tripped, and inspect the air filter—replace if dirty. Ensure all vents and outdoor exhaust pipes are clear of snow. If these don't restore heat, switch to temporary heating and call a pro. Do not attempt any gas or electrical repairs yourself.

Safety Boundaries: What You Can and Cannot Touch

Homeowners can safely check the thermostat, circuit breaker, air filter, visible vents, and condensate drain line (if accessible). These checks do not involve gas, high voltage, or combustion components. Do not attempt to: relight a pilot light on older furnaces if you smell gas, open the furnace cabinet to troubleshoot circuit boards or wiring, replace or bypass safety switches, or inspect the heat exchanger. If you detect a gas odor (rotten eggs), evacuate immediately and call your utility company from outside. For any internal component issues, a licensed HVAC technician is required.

Symptom-Based Troubleshooting Table

Decision Rules: When to DIY and When to Call

Follow this decision flow:

• If the thermostat display is blank → check batteries and breaker. If still blank → call pro.
• If the filter is visibly dirty → replace it. Wait 15 minutes. If heat resumes, done. If not → proceed.
• If outdoor exhaust pipes are snow-covered → clear them. If still no heat → check condensate drain for ice (high-efficiency models). If frozen, thaw safely (warm cloth) or call pro.
• If you have checked these and the furnace still doesn't ignite → the issue is likely internal (ignitor, flame sensor, gas valve, control board) and requires a pro. Diagnostic visit typically $80–$200 (editorial estimate, varies).
• If you smell gas at any point → stop and evacuate immediately.

Threshold: If heat hasn’t restored within one hour of safe checks, or indoor temperature falls below 55°F, activate temporary heating to protect pipes.

Temporary Heating and Preventing Frozen Pipes

While waiting for repair, set up portable electric heaters in a central room. Never use ovens or grills for heat. To reduce risk of frozen pipes: open cabinet doors under sinks, drip faucets (cold water, pencil-thin stream), and keep interior doors open to circulate heat. Learn more in our guide: How to Keep Pipes from Freezing When Your Heater Fails. Electric heater costs: running a 1,500-watt unit 24/7 can add $150–$300 to a monthly bill (editorial estimate, check local rates). Consider our Emergency Cost Tool to estimate total outage expenses.

Cost Guidance: What to Expect for Furnace Repair

Editorial cost estimates (not guaranteed quotes, actual prices vary by region, season, and contractor):

• Diagnostic service call: $80–$200 (after-hours: up to $300).
• Common repairs (ignitor, flame sensor, thermostat): $150–$700.
• Major repairs (blower motor, gas valve, control board): $800–$2,500+.
• Furnace replacement: $5,000–$15,000+ depending on efficiency, size, and installation complexity.

Use our Repair or Replace Calculator if your furnace is over 10 years old and repair exceeds 50% of replacement cost.

Contractor Checklist: 7 Questions Before You Approve Work

When the technician arrives, ask:

1. What is the exact diagnostic fee and how is it applied? (Is it credited toward repair?)
2. What is the specific failed part, and can you show me? (Ask for proof; a reputable tech will explain.)
3. Is this repair covered under warranty? What are the labor costs separately?
4. Are there multiple repair options, and what are the pros/cons of each? (e.g., oem vs generic parts)
5. What is the total all-in price before tax, and is there an emergency surcharge?
6. If a replacement is recommended, what are the SEER/efficiency ratings and warranty terms of the proposed unit?
7. Can you provide a written estimate with parts, labor, and timeline before starting?

Compare contractors on HVACDatabase: Contractor Comparison or Find a Local Pro.

Local Climate Considerations

Cold climates (northern regions): Pipe freeze risk is high. Take immediate freeze prevention steps. Furnace failures in sub-zero temps may require emergency priority service—expect higher after-hours charges. Coastal and humid areas: Reduced furnace use? Check for rust or corrosion that could cause electrical failures. Older homes: Ductwork and wiring may be incompatible with newer high-efficiency furnaces; discuss with contractor. Find heating repair pros in Chicago (example), or search your city at HVACDatabase.

Frequently Asked Questions

1. Why does my furnace blow cold air sometimes?
It could be a dirty air filter, thermostat fan set to “on” instead of “auto,” or an ignition problem. Check filter and thermostat first; if cold air persists, call a pro.

2. Can I use my fireplace or space heater if the furnace is out?
Yes, if safe. For fireplaces, ensure damper is open and chimney is clear. Use portable electric heaters with tip-over protection, keeping them 3 feet from flammables. Never use a gas oven or stovetop.

3. How long does an emergency furnace repair usually take?
Technicians carry common parts; a simple sensor replacement may take under an hour. Major repairs could require parts ordering, taking 1–3 days. Always ask upfront.

4. What temperature will cause pipes to freeze in a house?
Pipe freeze risk increases when indoor temperatures fall below 55°F, but actual freezing can occur at 20°F or lower ambient temperature depending on insulation and exposure. Act before indoor temp drops below 50°F.

5. Does homeowners insurance cover furnace failure damage?
Insurance typically does not cover the furnace repair itself, but may cover resultant damage like burst pipes and water damage if you took reasonable precautions. Check your policy.