A furnace that will not run, or runs but does not heat, can usually be sorted into a short list of causes. Mr. Air handles diagnosis and repair for home heating equipment, with safety placed ahead of speed.
Furnaces depend on a sequence: a call for heat from the thermostat, airflow, ignition, a burner or heating element, and a blower that moves warm air through the ducts. A break anywhere in that sequence can leave the house cold.
These are the symptoms people describe most often when they ask for heating repair.
Two details help a lot when you ask for heating repair: the type of fuel the furnace uses and whether the thermostat is calling for heat. Mention any codes or blinking lights you can see through the furnace's viewing window, as well as recent changes such as a filter swap or a power outage.
Fuel-burning heating equipment produces carbon monoxide, and a problem with a gas furnace is not always visible. A properly working furnace vents combustion gases outside. If a carbon monoxide alarm sounds, leave the house and call 911 or the gas utility from outside, as laid out in our guide to carbon monoxide safety and furnaces.
If you smell gas, do not operate switches, lighters or phones inside. Leave and contact the gas utility or emergency services from a safe distance. Neither situation is a do-it-yourself repair.
Working on gas lines, burners, venting and heat exchangers requires trained professionals. What you can do safely is limited and listed in our guides: check the thermostat, the breaker, the filter and whether the furnace switch is on.
A technician starts by observing the failure: what the thermostat is calling for, whether the blower starts, whether the ignition sequence begins and where it stops. Modern furnaces often show a diagnostic code that narrows the search considerably.
From there the work follows the evidence. Cleaning a flame sensor, replacing an ignitor or fixing a pressure switch problem is very different from replacing a blower motor or diagnosing a cracked heat exchanger. Each finding should come with the reason it matters and a clear statement of the options.
If the equipment is old, you will also want to know how repair compares with replacement. Our guide to how long an HVAC system lasts lays out the factors, and the heat pump installation page explains one alternative to a furnace.
Be ready for the possibility that the answer is not a single part. Older furnaces can have several worn components at once, and the honest assessment may be a short list of options with the tradeoffs for each, from a limited repair to planning for replacement.
Airflow trouble is behind a large share of furnace complaints. A clogged filter forces the blower to work harder and can cause the furnace to overheat and shut down on a safety control. Replacing it is among the simplest maintenance tasks in the house, and choosing the right one is covered in our guide to furnace filters and MERV ratings.
Closed or blocked vents, collapsed ductwork and dirty blower components cause similar symptoms, and a heating visit often includes looking at the whole air path rather than the furnace alone.
A furnace that sits idle through summer should be checked before the first cold spell, not after. A seasonal tune-up covers cleaning, safety checks and wear inspection, and it is described in what an HVAC tune-up includes. You can arrange it through our maintenance plans and tune-ups service.
Heating repair requests can be sent through the form with the No heat option selected.
Start with the thermostat mode and setpoint, then check the furnace power switch, the breaker and the filter. If those are fine, a safety control, ignition or control board issue may be responsible and needs a technician.
Follow the manufacturer's label for your specific unit, and stop if you smell gas. Many modern furnaces have no pilot light. When in doubt, request service rather than guess.
Leave the house immediately and call 911 or the gas utility from outside. Do not turn anything on or off inside, and do not go back in until emergency responders say it is safe.
Yes. Restricted airflow can cause overheating, which trips a safety limit and shuts the burners off. Replacing the filter is one of the first things to check.
Tell us what your system is doing and we will follow up with next steps.