No heat on a cold night is the call we take first.
Furnace and heat pump repair for homes across the Oklahoma City and Tulsa metros. Some heating faults are a comfort problem and some are a safety problem, and the first thing worth knowing is which one you have.
No heat right now?
If you smell gas, leave the house first and call from outside. Otherwise, call and describe what the furnace is doing.
(800) 555-0120 Request service- We treat heating emergencies as urgent, day or night.
- Diagnosis and a price before anything is opened up.
- If it is a safety issue, we tell you plainly.
Why is my furnace not heating? The common causes are a thermostat problem, a clogged filter choking airflow, a tripped safety control, a failed igniter or flame sensor on a gas furnace, or a pilot or gas supply issue. Most are a straightforward repair. But a furnace is also the one appliance in your home that burns fuel, so a small number of heating faults are safety matters, cracked heat exchangers and carbon monoxide among them, and those have to be ruled out first. This page tells you which is which.
A furnace almost always fails on the coldest night, because that is when it is running hardest. Most of the time it is a comfort problem with an ordinary repair behind it. Occasionally it is a safety problem, and because a furnace burns gas, that possibility gets dealt with before anything else. The rest of this page keeps those two apart so you know when to wait and when to act.
The safety checks that come before everything else
If any of this is happening, stop and get to safety
- You smell gas, a rotten-egg or sulphur smell. Do not touch light switches or anything electrical. Leave the house, take everyone with you, and call your gas utility's emergency line and 911 from outside. Call us after you are safe.
- Your carbon monoxide alarm is sounding. Get everyone outside into fresh air and call 911. Carbon monoxide has no smell, and this alarm is the only warning you get. If you do not have one on each floor, that is the most important thing you can buy this winter.
- You feel dizzy, nauseous or have a headache that eases when you leave the house. Treat it as possible carbon monoxide. Get outside and call for help.
- You see soot, scorching, or a flame that is yellow and lazy rather than crisp and blue. Shut the furnace off and call. A gas flame should burn blue.
None of this is meant to frighten you, and the great majority of heating problems are nothing like this. But a furnace burns fuel, so these come first, every time.
The safe checks before you call
If none of the safety signs above are present, a few ordinary things account for a real share of heating problems, and they are all safe to check.
- The thermostatSet to heat, turned up above room temperature, and not stuck in a schedule you forgot about. Replace the batteries if it takes them. A dead thermostat is indistinguishable from a dead furnace.
- The filterA clogged filter chokes airflow, and on a furnace that can trip a safety limit that shuts the whole thing down to prevent overheating. Hold it to a light. If you cannot see through it, replace it and give the furnace a few minutes to reset.
- The furnace switch and breakerFurnaces have a switch that looks like a light switch, usually on or near the unit, that gets flipped off by accident. Check it is on, and check the breaker has not tripped. If the breaker trips again after one reset, leave it off and call.
- The furnace door panelMost furnaces will not run unless the front panel is fully seated, because a safety switch behind it has to be pressed in. If someone changed a filter and did not click the panel back on, that alone stops it.
Beyond that, you are into igniters, flame sensors, gas valves and control boards, which are not homeowner territory. Anything involving the burners or the gas supply should be left to someone with the instruments to test it safely.
What you are noticing, and what it points at
| What you notice | Safe next step | What it usually falls under | What has to be checked |
|---|---|---|---|
| Furnace runs but blows cool air | Check the thermostat is on heat, not just fan | Igniter, flame sensor, gas supply, or the control giving up and stopping | Ignition sequence, flame signal, gas pressure |
| It starts, runs briefly, then shuts off, over and over | Change the filter, then call if it continues | Overheating on a safety limit, often airflow, or a flame sensor | Airflow and temperature rise, flame sensor, limit history |
| Nothing happens at all | Check the switch, breaker and door panel | Power, the door safety switch, thermostat, or a control board | Voltage, the switches, control board |
| Clicking, then nothing lights | Leave it and call | A failed igniter or a control trying and giving up | Igniter resistance, ignition sequence |
| Loud bang or boom when it lights | Shut it off and call promptly | Delayed ignition, gas building before it lights | Burners, gas pressure, ignition timing |
| Blower runs constantly and never stops | Check the thermostat fan setting is auto, not on | Thermostat setting, a stuck fan relay, or a limit | Fan settings, relay, limit switch |
| Yellow, flickering flame instead of blue | Shut it off and call | Incomplete combustion, a real safety concern | Combustion, heat exchanger, venting |
| Some rooms warm, others cold | Check registers and returns are open | Duct design or leakage more often than the furnace | Room-by-room airflow, duct condition |
Categories, not diagnoses. Anything touching the burners, the flame or the venting is a safety check, not a guess.
What a real diagnostic visit includes
You describe it, we listen
What it is doing, what changed, and whether anyone has felt unwell. History matters, and so does the safety picture.
Combustion and safety first
On a gas furnace, the burners, the flame, the heat exchanger and the venting are checked before anything else. This is the part a rushed diagnosis skips, and it is the part that keeps you safe.
Ignition and controls
Igniter, flame sensor, gas valve, control board, tested with instruments rather than swapped on a hunch.
Airflow
Filter, blower, temperature rise across the furnace. Poor airflow trips safety limits and imitates a heating fault.
The findings, plainly, with a price
What failed, what it costs, and whether it is a repair or a safety issue that changes the conversation. You approve before work starts.
Questions worth asking
- Did you inspect the heat exchanger, and what did you find?
- Is this a comfort problem or a safety problem?
- What did you measure, and what were the readings?
- Is this repair likely to hold, or is it buying one more winter?
- What does the repair cost against a replacement, and what would you do here?
- Is the part under a manufacturer warranty I already have?
Repair or replace?
The full framework is on its own page, but heating has one factor cooling does not: a cracked heat exchanger. That is the metal wall that keeps combustion gases, including carbon monoxide, separate from the air you breathe. When it cracks, the furnace is usually condemned rather than repaired, because a patched heat exchanger is not a safe heat exchanger. On a furnace near the end of its life, that is the moment replacement stops being a choice. Short of that, a furnace with one failed part and a sound heat exchanger is very often worth repairing.
Questions and answers
My furnace is blowing cold air. What is wrong?
Start with the thermostat: if the fan is set to on rather than auto, the blower runs even when the furnace is not heating, and that feels like cold air from the vents. Switch it to auto and see whether warm air returns when it calls for heat.
If it still blows cold, the furnace is trying to run the fan without successfully lighting, which points at the igniter, the flame sensor or the gas supply. That is a service call. It is not dangerous to leave off while you wait, so turn the heat off until someone can look at it.
Is a cracked heat exchanger really that serious?
Yes. The heat exchanger is the sealed metal wall that keeps combustion gases, including carbon monoxide, away from the air circulating through your house. A crack can let those gases into your living space, and carbon monoxide is odourless and can be deadly.
This is why a reputable technician condemns a cracked heat exchanger rather than patching it, and why we would rather lose the repair than put a compromised one back into service. It is also why a working carbon monoxide alarm on every floor is not optional.
How much does furnace repair cost?
It depends on the part. A flame sensor, an igniter or a thermostat sits at the low end. A gas valve, an inducer motor or a control board is in the middle. A cracked heat exchanger or a failed blower on an older furnace is the point where replacement usually deserves a serious look.
What we commit to is a diagnosis and a fixed price before work starts, with the price holding unless we find something new and you approve it.
Why does my furnace keep shutting off before the house is warm?
That pattern, starting, running briefly, then stopping, is called short cycling, and the most common cause is overheating on a safety limit. The furnace is protecting itself. The usual culprit is restricted airflow, and the usual cause of that is a clogged filter, so change the filter first.
If a fresh filter does not fix it, the cause could be a failing flame sensor, a limit switch, or a system that is oversized for the house. Those need a technician, but changing the filter costs you nothing and solves it more often than you would think.
Do I need a carbon monoxide detector if my furnace is newer?
Yes, regardless of the furnace's age. Any fuel-burning appliance can produce carbon monoxide if something goes wrong, and a newer furnace is not immune to a venting problem or a failed component. A detector is inexpensive and it is the only warning you get for a gas you cannot smell.
Put one on every floor and outside sleeping areas, and replace them on the schedule printed on the unit, because the sensors do wear out.
How quickly can someone come out for no heat?
Heating emergencies are treated as urgent, especially in a hard freeze and especially if there is an infant, an elderly person, or someone with a medical condition in the house. Say so when you call and it moves you up the order.
What you get is a real arrival window rather than a vague promise, and a call if it slips. If you smell gas or suspect carbon monoxide, that is not a service call, it is an emergency: leave the house and call 911 and your gas utility first.
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Warm the house back up.
Tell us what the furnace is doing and we will tell you whether it needs someone tonight or whether it can wait until morning.
(800) 555-0120