When your air conditioner runs for much of the year, it’s easy to forget about the furnace until the first cold evening. A few checks before the weather changes can help you spot problems while there’s still time to schedule service.

Gas furnace maintenance comes down to four basics: checking the filter, keeping airflow paths clear, testing the heat, and arranging an annual professional inspection. Here’s what you can do yourself and what to leave to a technician.

If you smell gas or a carbon monoxide alarm sounds: Get everyone outside immediately. If you suspect a gas leak, don’t operate the thermostat, light switches, or garage door opener. From a safe location, call 911 and, for a suspected gas leak, Southwest Gas at 877-860-6020. Stay outside until emergency responders say it’s safe to return.

1. Check the Air Filter Before Heating Season

Your furnace may have been off all summer, but that doesn’t mean its filter is clean. In many central heating and cooling systems, the air conditioner and furnace share a blower and filter. That filter has been collecting dust every time the AC runs.

A dirty filter restricts airflow. That can leave rooms feeling chilly, make it harder for the furnace to distribute heat, and contribute to overheating and repeated shutdowns.

Check the filter monthly while the system is in regular use. Many basic disposable filters need replacing every one to three months, but there isn’t one schedule that fits every home. The filter type, equipment, pets, dust, and how often the system runs all matter. Thicker media filters may have different replacement intervals, so follow the manufacturer’s instructions.

When replacing an accessible filter:

• Turn the system off and follow the equipment’s instructions.
• Use the correct filter size and a filtration rating suitable for your system.
• Position the airflow arrow toward the furnace or air handler.
• Replace disposable filters. Only wash a filter if it is designed to be reusable, and let it dry completely before reinstalling it.

If you’re considering a filter with a higher filtration rating, check that your system can accommodate it. A filter needs to capture particles without restricting airflow more than the equipment can handle.

2. Keep Vents, Returns, and the Furnace Area Clear

Heated air needs a clear path through your home. Supply registers deliver warm air to the rooms, while return grilles draw air back toward the system.

Check that furniture, rugs, and curtains aren’t covering either type of opening. Vacuum surface dust from accessible grilles, and avoid closing multiple registers to redirect heat into other rooms. Restricting airflow can interfere with furnace operation.

If one bedroom stays cold while the rest of the house warms up, mention that when you schedule service. The problem may involve airflow or ductwork rather than the furnace’s ability to produce heat.

The space around the furnace matters, too. Keep boxes, laundry, cleaning products, and other stored items away from the equipment. Follow the clearance requirements in the manual or on the equipment label, and leave furnace-closet ventilation openings unobstructed.

The furnace’s exhaust vent serves a different purpose from the room vents: it carries combustion gases outdoors. If you notice a loose, damaged, or corroded exhaust connection, stop using the furnace and arrange service. Leave exhaust repairs and inspections that require attic or roof access to a qualified technician.

3. Test the Heat Before You Need It

Give your furnace a trial run before the first cold night. Set the thermostat to Heat, then raise the temperature a few degrees above the room temperature. If the thermostat uses batteries, check them, and make sure a programmed schedule or away setting isn’t overriding your adjustment.

Set the fan to Auto for this check. In the On position, the fan may keep circulating room-temperature air between heating cycles, making it feel as though the furnace is blowing cold air.

Allow for the system’s normal startup delay, then pay attention to how it runs:

• Does warm air come through the registers?
• Does the house begin reaching the temperature you selected?
• Does the furnace keep shutting off before the house warms up?
• Are there unfamiliar noises or lingering odors?

A brief dusty smell during the first seasonal startup can come from dust heating up on components. An odor that persists or gets stronger needs attention. If you notice a burning-plastic or electrical smell, turn the system off and have it inspected. If you smell gas, leave immediately without touching the controls.

Repeated starting and stopping is often called short cycling. A dirty filter or blocked vents can contribute, but ignition or control problems may also be involved. If the basic airflow checks don’t resolve it, turn the furnace off and schedule service. Repeatedly resetting it won’t address the underlying problem.

4. Schedule a Professional Furnace Inspection Each Year

Las Vegas has a shorter heating season than many parts of the country, but limited use doesn’t tell you whether a gas furnace is operating safely. An annual inspection gives a technician a chance to check the components you can’t evaluate by changing a filter or testing the thermostat.

Schedule the visit before you expect to use the heat regularly. When booking, ask what the service includes. Depending on the equipment and manufacturer’s requirements, furnace maintenance may involve:

• Inspecting the heat exchanger and exhaust venting.
• Checking gas connections, gas pressure, and burner operation.
• Inspecting the ignition system and flame sensor.
• Checking the blower, electrical connections, and safety controls.
• Testing the heating cycle and checking performance.
• Cleaning components as needed and explaining any recommended repairs.

If you had an AC tune-up during the summer, check the service record before assuming the furnace was covered. The systems may share a blower and ducts, but cooling service doesn’t necessarily include the burners, ignition system, or furnace exhaust.

Leave gas adjustments, burner work, and internal electrical repairs to a qualified HVAC technician.

Working carbon monoxide alarms are another important precaution. Install them on each level of the home and outside sleeping areas, following the manufacturer’s placement instructions. Test them monthly and replace batteries or the alarms as directed. Carbon monoxide has no smell, and alarms do not replace regular furnace maintenance.

Common Questions About Gas Furnace Maintenance

What should I check if my gas furnace isn’t producing heat?

Check that the thermostat is set to Heat and that the selected temperature is above the room temperature. Check the batteries if applicable, and confirm that the furnace’s accessible power switch hasn’t been turned off. A gas furnace still needs electricity to operate.

A clogged filter can also contribute to shutdowns. If these checks don’t identify the problem, schedule service rather than adjusting gas valves or repeatedly resetting the equipment.

Why is my furnace running but not heating the house enough?

Restricted airflow, thermostat settings, duct problems, or a furnace fault can all affect how well your home heats. Note whether the problem affects one room or the whole house, and whether the air coming from the registers feels warm. Those details can help a technician narrow down the cause.

The symptom alone doesn’t tell you what the repair will involve or how much it will cost.

Does every gas furnace have a pilot light?

No. Older furnaces may have a standing pilot light, but newer models commonly use electronic ignition. Not seeing a continuous flame doesn’t necessarily mean there’s a problem.

Check your furnace manual to find out which system you have. Never try to light an electronic ignition furnace with a match. If an older furnace’s pilot repeatedly goes out, have a technician investigate the cause.

Does my furnace need annual service if I rarely use it?

Yes. Annual professional service is still recommended for gas furnaces, even in homes where the heat runs infrequently. Low use doesn’t confirm that the venting, ignition, and safety controls are working properly. Having those components checked before heating season helps you prepare for the nights when you do need the furnace.

Furnace Maintenance and Heating Help in Las Vegas

If your furnace is due for maintenance, isn’t warming the house evenly, or keeps shutting off, contact Sahara Air Conditioning & Heating. Let us know what you’ve noticed and which checks you’ve already made.