Why is my furnace running but blowing cold air?
Start with the thermostat setting, the filter and the gas valve. A dirty flame sensor, a failed igniter or an overheated unit can also cause it. If those checks fail, stop and have a provider look.
A furnace that will not start, blows cold air, or shuts off after a few minutes is more than a comfort problem. When winter frost sets in, a cold house can put your pipes at risk fast. That is why timing matters so much here.
Secretsun Heating & Air is a referral service. We do not repair furnaces ourselves. We connect homeowners in Hammond and the Hammond area with independent local providers who handle heating and cooling work. This page shows what to check yourself, what happens as the hours pass, and what a repair usually costs, so you can ask smart questions and get a written quote before any work begins.
Smell Gas? Stop and Step Outside
Rotten-egg smell? Do not hunt for the source. Walk everyone out of the house. Do not flip switches, light anything, or use a phone inside. From outside, call the gas utility or 911. Go back in only when they say it is clear.
Carbon Monoxide Is a Separate Alarm
If a CO alarm sounds, or you feel headachy and dizzy near the furnace, get outside and get fresh air. Do not silence the alarm and carry on. A cracked part or a blocked flue can cause this. That is a job for a pro.
The First Hour: Check, Then Stop
Most no-heat problems start with something simple. Spend ten minutes on the easy stuff. Stop the moment a check points to something inside the furnace cabinet.
Thermostat
Set it to heat and raise the target five degrees above room temperature. Swap the batteries if the screen is dim or blank.
Switch and Breaker
Look for a wall switch near the furnace. It looks like a light switch and gets bumped a lot. Check the breaker too. Flip it once. If it trips again, leave it off.
Filter and Vents
Pull the filter and hold it up to a light. If you cannot see through it, swap it. A clogged filter can make a furnace overheat and shut itself down. Open every vent and clear anything blocking the returns.
Gas Valve and Pilot
The gas valve handle should sit parallel to the pipe. On an older pilot-style unit, follow the lighting steps on the label. If the flame will not stay lit, stop there.
What Happens Hour by Hour
This is why you should not wait on a stubborn furnace.
Hours One to Six
The house loses heat slowly at first. Older frame houses leak more, so rooms far from the furnace cool first. This is a good window to line up a provider while the fix is still just a repair.
The First Night
During deep frost, indoor temps can sink toward the 40s. Pipes on outside walls and in the basement are most at risk. Open the cabinet doors under sinks and let one faucet drip. Keep any space heater away from curtains and bedding.
Day Two and Three
Cold walls pull in damp air. Ice can build inside pipes, and some will split. A small furnace repair can turn into a repair plus plumbing and drywall.
After Day Three
Water damage, mold and a stressed system add up. Some policies may cover sudden damage, so check your policy. Providers can often help document damage for a claim.
Signs Your Furnace Needs Repair
You do not need a dead furnace to need help. Watch for these:
- Bangs, rattles or a loud squeal when it starts
- A yellow or flickering flame instead of steady blue
- Short cycling, where it kicks on and off every few minutes
- Cold rooms next to hot ones
- Heating bills climbing with no change in habits
- A burning smell that lingers past the first run of the season
What a Repair Visit Looks Like
A provider starts with safety checks, then tests the thermostat, ignition, flame, airflow and controls. They find the fault, explain it in plain words, and give you a price. You should hear that price before any part comes out.
Common Furnace Repairs
Most visits come down to a short list:
- Igniter or pilot assembly
- Flame sensor cleaning or swap
- Blower or inducer motor
- Control board
- Limit switch or pressure switch
- Cracked heat exchanger, which is the serious one
Repair or Replace Your Furnace?
Think about age first. Past 15 years, parts get harder to find and the next failure is never far off. Add up the repair quote. If it is near half the price of a new unit, replacement is worth pricing. A cracked heat exchanger usually means replacement.
If you have been typing furnace replacement near me into a search bar, ask the provider to quote both a repair and a new unit. Compare them side by side.
Questions to Ask the Provider
Keep these handy when the phone rings:
- Is there a diagnostic fee, and does it apply to the repair?
- Is the price in writing before work starts?
- Are parts and labor warranted, and for how long?
- Can you check availability for tonight?
- Are you licensed in my state?
Quote in Writing
A written quote protects you. It lists the part, the labor and the total. Keep it. If the scope changes mid-job, ask for an updated one. Providers who handle HVAC service well are happy to do this.
What's Included
Safety Checks
Gas smell, carbon monoxide risk, venting and flame are looked at before anything else gets touched.
Fault Diagnosis
The provider tests ignition, airflow and controls to find the real cause, not just the symptom.
Parts Repair
Igniters, sensors, motors and boards are swapped or fixed, based on your written quote.
Test Run
After the fix, the furnace is run through a full cycle to confirm steady heat and safe operation.
What Furnace Repair Costs
Prices vary by job, part and home. These are typical U.S. ranges, not quotes. Labor, furnace age and after-hours scheduling all move the total, so always get the number in writing first.
| Item | Typical range | Notes |
|---|---|---|
| Diagnostic visit | $75 – $200 | Often applied to the repair if you proceed |
| Igniter or pilot part | $150 – $400 | Common on cold-start failures |
| Flame sensor | $100 – $300 | Often just needs cleaning or a swap |
| Blower or inducer motor | $400 – $1,500 | Varies by motor type and brand |
| Control board | $300 – $800 | Price depends on make and model |
| Heat exchanger | $1,500 – $3,500 | Often leads to a replacement quote |
How It Works
Check the Basics
Run through the thermostat, switch, breaker and filter. Stop at the furnace cabinet and do not open it.
Call to Check Availability
Request a callback to check provider availability. Many providers can respond quickly when a house is cooling.
Get a Written Quote
Ask for the part, labor and total in writing before the work begins.
Approve the Repair and Test
Say yes when the quote makes sense, then watch the furnace complete a full cycle.
Why Call Secretsun Heating & Air
Timing Protects Your Pipes
Acting while the house is still warm keeps a simple repair from becoming a plumbing and drywall bill.
Local Providers
Providers in our network know area winters and housing, from old frame homes to ranches.
Plain Answers
You get clear explanations and a written quote before any work starts.
No Obligation
Request an estimate, compare it, and decide. You are never locked in.
Other Services
Need furnace repair services in Hammond?
Tell us what your system is doing. Request a callback to check provider availability, or send a request and a local provider will follow up.
No obligationQuestions
Furnace Repair Services FAQ
How long can a house go without heat in winter?
It depends on the outdoor temperature and how well the house holds heat. In deep frost, pipes can be at risk within a night or two, so act early.
Is it worth repairing an old furnace?
Often yes, if the repair is small. If the unit is past 15 years or the quote nears half the price of a new one, ask for a replacement quote too.
Contact
Reach a local provider
Tell us what your system is doing. Request a callback to check provider availability, or send a request and a local provider will follow up.
No obligation