Checklist for Troubleshooting Gas Furnace Problems

If you have a forced-air furnace, air gets pulled in from the rooms, past a filter, and into the furnace to get heated. A typical forced-air furnace burns either gas or oil and then a heat exchanger transfers the heat to filtered air, keeping the hot flue gases safely separated. The warm air then gets blown back into the rooms through supply ducts and registers.

There’s a lot more to it than that, but you get the gist. For maximum furnace efficiency, it’s important to schedule professional maintenance in the fall, regularly change air filters, and keep a general eye on things.

While untrained adults can perform basic furnace maintenance, such as replacing air filters and general cleaning, only trained and certified technicians should service, repair, or replace heating equipment.

Not only is heating equipment dangerous due to combustion gases and electrical components, DIY repairs can void the remainder of any warranties you may have. Always follow the information in your owner’s manual exactly and call a qualified service technician if you have any questions or concerns.

Basic Preventative Furnace Maintenance

• Check your air filter every month during the heating season. Replace or clean it as necessary.
• Schedule professional heating maintenance every year, ideally in the fall.
• Examine duct system for excessive dirt and leaks.
• Make sure the dampers in all your registers are wide open. Never block or close vents and registers.
• Never store anything near your furnace, especially paints, detergents, household cleaners, gasoline, combustible materials, and any products that release fumes, which could lead to early heat exchanger and vent system deterioration — not to mention the risk of damage, personal injury, or loss of life.
• Learn more tips for preparing your furnace for winter.

Checklist for Troubleshooting Gas Furnace Problems 

A professional inspection and tune-up should be performed by a qualified technician at the start of every heating season. Regular maintenance and troubleshooting are essential for keeping your furnace functioning safely and efficiently.

Do not attempt any other repairs or adjustments yourself. Bell Brothers can take care of any questions or problems you may have.

No Heat

• No power

Check the breaker box and master switch for power. There may be an emergency off switch somewhere outside of the basement or furnace room and another one very close to the heating equipment. It’s normally just referred to as the “furnace switch.” Make sure power is on everywhere.

If you replace a fuse or reset a circuit breaker and the fuse blows or breaker trips again, do not restore electrical power to that circuit. Call a professional technician to troubleshoot and fix the problem.

• Defective thermostat

Clean the thermostat, replace the batteries, or replace the thermostat altogether.

Make sure the thermostat is set to “heat” and higher than room temperature. See owner’s manual for operating instructions.

• No gas

Make sure the gas safety shut-off valve near the furnace is in the “on” position (parallel with the pipe). If other gas appliances aren’t working either, check the shut-off valve near the main gas meter. Ensure all gas appliances and pilot lights are off before you turn the gas back on.

If the gas has been turned off, contact your gas company. If you have an oil or propane tank and it is low on fuel, contact your supplier.

• No filter

There must be a filter in place during operation. Some models won’t turn on if no filter is detected. Make sure the filter is clean and its arrows are pointing in the direction of the airflow.

• Blower door ajar

Similarly, some systems won’t turn on if the blower door is removed or ajar. Close the door securely to restore power. All panels must be securely fastened for safe operation.

If you notice any dirt or debris, now is a good time to clean it off.

• Pilot light

A pilot light is a small flame that provides ignition for the burners. It should stay lit 24/7. If your pilot light is out, no heat will be produced. Follow the instructions in your owner’s manual for relighting the pilot. If the pilot light doesn’t stay lit, contact a qualified technician.

Insufficient Heat

• Clogged filter

Check the filter and clean or replace it if necessary. Make sure it is installed correctly with the arrows pointing in the direction of the airflow. Learn how to properly check and change the furnace filter.

• Leaking air ducts

You can look for leaking air ducts by holding up a lit piece of incense around duct connections (while the system is on “fan” setting). The smoke will blow away if there is a leak in supply ducts or get sucked in if it is a return duct. According to Energy Star, 20-30 percent of the air that flows through our air ducts gets lost to leaks and poorly connected ducts.

Learn more about finding and sealing air ducts in your home. Work with the experts at Bell Brothers to inspect, seal, and insulate all the duct leaks in your home.

• Blocked registers

Go around your home and make sure all of your supply and return registers are open and unblocked. Never block HVAC registers, intentionally or not.

• Loose blower belt

If you have a belt-drive blower, you may want to inspect the belt and adjust or replace it as needed. Failing belts can cause squealing sounds, blower problems, and premature breakdowns. Contact a professional technician if you notice any problems with the blower belt.

• Burner flame

  

It’s a good idea to periodically check your furnace flame color and behavior. The flames should be a bright blue, although some very light yellow/orange tipping may be normal.

A healthy blue color indicates safe and efficient combustion. If the flames are any other color than blue or behaving irregularly, contact a qualified technician right away.

Noisy Operation

• Insufficient lubrication

Furnace components, such as shaft bearings may need to be lubricated. Call your servicer.

• Tight, loose, or aging belt

You may need to tighten, loosen, or replace your blower belt. Call your servicer.

Room Temperature Doesn’t Match Thermostat

• Wrong location

If your thermostat is near an air vent, window, or other heat source, it will turn off prematurely. Your actual room temperature will never reach the right setting if the thermostat is being warmed up by something nearby. Contact a professional to move the thermostat to a new location if necessary.

• Thermostat improperly installed

Follow thermostat troubleshooting instructions in your owner’s manual. If you have any questions, contact your local HVAC technician.

• Check balance

You want to make sure your thermostat is completely level, especially if it uses a mercury switch.

Gas Odor

If you smell gas, there could be a leak, loose connection, or broken gas line. Act immediately.

Follow these steps if you smell gas in your home:

• Do not try to touch light anything or touch anything electrical, including phones or light switches.
• Immediately evacuate everyone from the building and call your gas supplier from a safe distance. Follow the gas supplier’s instructions.
• If the gas supplier cannot be reached, call the fire department.

Safety Precautions

Do NOT rely on smell alone to detect leaking gases. Make sure you have working fuel gas and CO detectors installed according to manufacturer instructions.

If you smell any unusual odors near your furnace, shut down the unit and contact a licensed technician.

If you are experiencing headaches, nausea, fatigue, or dizziness, you may be exposed to carbon monoxide gas.

Furnace Troubleshooting Steps

1. Air filter should be clean and properly installed.
2. Make sure power is on at the breaker box and disconnect switches. Reset circuit breakers or replace blown fuses if necessary.
3. Check the thermostat for proper location and setting (“heat”). See owner’s manual.
4. Check the pilot light. If you need to relight the pilot, consult your owner’s manual.
5. Gas valve should be “on” (parallel with the pipe). Is gas turned on at the meter? Contact the gas company if you aren’t receiving any gas.

Shut down your unit and contact a professional immediately if you:

• Hear new, strange, or unfamiliar sounds.
• Smell strange odors.
• See condensation (water) on any surface of the furnace
• See damaged, deteriorated, or loose components

Keep your furnace looking brand new:

• Keep the enamel finish clean with regular soap and water.
• For grease spots, use household detergent.
• Lacquer thinner or other chemical cleaners may damage the finish

Periodically check your HVAC system for dirt or debris on any of the surfaces or components.

While it’s a good idea to clean and vacuum grilles, access panels, and the area around your furnace, do NOT try to clean furnace components yourself. Furnace cleanings should be left to a qualified professional.

Last Hope Furnace Reset

If you still haven’t solved your furnace problem, you may want to try one last reset before calling in the professionals:

1. Check the pilot light
2. Turn down the thermostat
3. Turn off the gas and power to the furnace
4. Re-light the furnace
5. Reset the furnace

If that didn’t solve your problem, don’t hesitate to contact Bell Brothers.

Remember, installation, service, and repairs must be performed by a licensed technician. During your annual furnace tune-up, our experienced technicians will check everything, including the burners, vent pipe, air ducts, operating performance, heat exchanger, and much more.

Contact Bell Brothers to schedule your fall furnace tune-up or a free in-home estimate on furnace repairs.

Our “No Surprise Guys” have been serving the Sacramento and Northern California area for more than 30 years. The price we quote is the price you’ll pay—guaranteed.