(707) 800-6287 |  Sonoma Napa and Marin Counties

Winter is upon us, and we depend on the furnace to create a cozy home during the festive season. We present 10 Common Furnace Problems (And How to Fix Them) in this blog post to help you if the heat doesn’t come through the vents. The solutions are kept simple and within the scope of safety. For anything but the obvious, a trained and certified furnace repair technician must be consulted for any services and repairs.


1) Lack of Regular Maintenance


Annual inspections and maintenance work are central to a trouble-free furnace. The best time is either at the end of the summer or the beginning of fall. If you neglected to have the furnace serviced for a few years, you could expect it not to respond. Most of the problems on this list can be prevented through annual inspections by a trained furnace technician.


2) Thermostat Problems


The thermostat is the control interface of the furnace. Ensure that the fans are set to AUTO, meaning that they will switch on and off as required for efficient heat distribution throughout the house. If batteries power the thermostat controller, check that they are not run down – it is good practice to replace the batteries during the annual inspection. See that the correct temperature is set on the thermostat, and it’s not set to OFF or COOL. A temperature setting too close to the ambient temperature will not turn on the furnace.


3) Dirty or Clogged Filters


The air filters prevent dust, debris and other pollutants from blowing into the house through the furnace ducts. The filters become clogged with everything in the air, preventing clean air from flowing through the filter into the room. Regular cleaning or replacing the filters is necessary and easily performed, often outlined graphically in the owner’s manual.


4) Pilot Light


A bad pilot light will cause problems with the efficient functioning of the furnace, or it may indicate other issues. A quick visual inspection will resolve whether the pilot light is the culprit. It should be burning brightly. Any flickering or discoloration, especially towards yellow, may indicate excessive carbon monoxide in the furnace. If, however, the pilot light is out, follow the instructions in the manual to relight it, but do not repeatedly perform this procedure. If the pilot light is suspect, turn off the gas and contact the furnace repair technician. Never attempt to fix a pilot light yourself.


5) Frequent ON/OFF Cycling


A furnace that continuously turns on and off indicates there is something wrong. The most common causes are a faulty thermostat, clogged air filters or improper airflow. Check the filters and the thermostat for the apparent problems, as mentioned above.


6) Blower Runs Continuously


The cause can be that the blower is set to ON, not AUTO, on the thermostat, or the limit switch is malfunctioning. Verify the setting on the thermostat. Otherwise, the limit switch is causing the blower to run continuously. Only a furnace technician should attempt to replace the switch.


7) Noises


A furnace is not quiet, but it must not sound like a steam locomotive. The cause of any rattling, pinging or screeching sounds should be cause for concern. Screeching noises often indicate that the blower belt is frayed or damaged and needs replacing; grinding sounds could be caused by worn-out ball bearings in the electric motor, and rattling noises are probably loose duct panels. Whichever the cause, get a furnace technician to inspect the system.


8) Leaking Water


It seems counter-intuitive, but a properly working furnace generates a fair amount of water. Most of this is in the form of condensate. This water is typically drained away through pipes. If water puddles are present around the furnace, it probably means that the pipes are clogged or have developed a leak. Only a technician should investigate the cause.


9) Inspect the Gas Line


This line is usually the number one reason why a furnace won’t heat up. There are many reasons why gas can’t reach the furnace, ranging from forgetting to open the valve to the gas company shutting it off for maintenance works in the area. We recommend a visual check of the valves and lines and a phone call to the gas company before calling the furnace technician.


10) The Furnace is Busted


A furnace has a finite working life, usually fifteen to twenty years. It will be subjected to normal wear and tear during those years, despite annual inspections and services, which will eventually cause major components to fail or break. A cracked heat exchanger is common, especially when the furnace has worked very hotly for prolonged periods and then subjected to rapid cooling. A reliable HVAC technician will provide an accurate assessment and propose a solution based on the overall condition of the furnace.


We have to repeat – annual inspection and maintenance of the furnace will significantly reduce the occurrence of breakdowns and mitigate furnace repair calls. Please do not wait until your gas furnace breaks before calling your technician. Also, do not attempt to repair the furnace yourself.