Common Problems With Furnaces & The Repairs It Takes to Fix Them

January 10, 2024

Here are some tips on how you can fix common problems with furnaces.

Furnaces play an important part in keeping homes warm and cozy; if they start acting up or start having problems, however, this can be alarming.

Common Problems With Furnaces & The Repairs It Takes to Fix Them
Photo by Kateryna Babaieva

Common Problems With Furnaces & The Repairs It Takes to Fix Them

    There are some simple furnace problems you can easily resolve yourself, while others require professional assistance. Common examples of self-fixable issues with furnaces include rumbling or squealing noises that indicate problems with airflow, power supply, pilot light or thermostat settings.

    1. Thermostat Issues

    The thermostat sends signals to your furnace that help it heat your home. If the thermostat is malfunctioning or nonfunctional, this could cause your system to malfunction or stop functioning altogether. 

    According to the pros at, you should check its battery and change it if necessary; also trace all wires leading to it to ensure they're undamaged or disconnected. Last but not least, you should make sure it's level on its wall mount with its cover off as this ensures proper functioning.

    Pilot lights are big components of furnaces as they enable power production and heat generation, but they also directly communicate to your thermostat, itself. If your pilot light becomes discolored or completely out, this indicates there is a gas issue that should be fixed immediately by an expert.

    If the blower fan is running continuously, this could indicate either that your thermostat is set to continuous fan mode or there is an issue with its fan limit control switch. To quickly address this problem keep the blower fan running only when heating mode is active on your system. Simply switch it over to auto mode so your blower fan runs only then!

    2. The Pilot Light Is Out

    If your furnace is cycling between "On" and "Off," this could indicate various causes. These could include clogged filters, thermostat issues, or mechanical issues; or perhaps it has heard strange rumbling, squeaking, or rattling noises that seem out of the ordinary - call in a professional for inspection and repairs as soon as possible.

    If your gas furnace is an older model, its pilot light may go out unexpectedly and shut it off altogether. However, fixing this is usually simple, according to these instructions - first ensure the power switch is set to "On". Next, open up its front panel and look for a small knob labeled "pilot light" or "light." Turn this knob to its own position before holding a lighter above it - should a flame appear, it indicates loose thermocouples or fault in your unit's thermocouple system.

    A thermocouple is a safety feature designed to cut off natural gas flow if the pilot light goes out, located near and connected to your furnace's gas valve. If it becomes defective, however, its replacement should be performed.

    Potentially, there may be an issue with the gas supply in your area. Your local grid may have reached capacity and temporarily reduced pressure for other customers - in such an instance, your gas company will likely reset your pressure accordingly.

    3. The Blower Fan Is Not Working

    Faulty furnace blower fans are an often overlooked source of expensive repair bills; to protect you and keep costs to a minimum, check and replace filters regularly, clean off dust from blowers as needed and maintain them when possible.

    Another possible reason that your blower might not be working is if it has become clogged or blocked due to debris such as dirt or furniture that has been placed directly in front of vents. In such an instance, remove these objects to allow airflow without overtaxing your heating system.

    The pilot light is a small flame used to ignite gas and convert it to heat for use by your furnace. Normally it should be bright blue; if its hue changes to yellow or orange it could indicate that something has gone amiss and should be addressed immediately by professionals like Miller's Home Comfort.

    If the pilot light remains illuminated but your furnace doesn't produce heat, there could be an issue with either its pressure switch or thermocouple. An experienced furnace technician like those at Polansky Heating should examine them both to identify what's causing it, so contact them using the following information:

    Polansky Heating & Air
    2000 W Loop 340 #105, Waco, TX 76712
    1(254) 218-3321

    4. The Fan Limit Control Switch Is Not Working

    Fan limit control switches are essential components to help prevent your furnace from overheating when in operation. They monitor both the blower fan and gas valve temperature settings to ensure they're within acceptable parameters; should air become too hot for their temperature thresholds, the switch trips off, shutting down your furnace and locking its fan until things cool off - an invaluable protection against overheating which could cause irreparable damage to both it and your home.

    One common cause of fan limit switch tripping is a dirty filter. Make sure that you change out the filter regularly, open all vents and registers, and ensure adequate air movement throughout your home. Resetting or replacing may also be necessary if the fan limit switch continues to trip.

    When replacing a limit switch, you must find one suitable for your model. There are two kinds: electromechanical and solid state. Older electromechanical switches feature a probe that extends into the plenum (the box attached to ductwork that distributes air throughout your home), while newer solid-state ones mount onto plates that screw onto burner housing and are disk-shaped - each type comes equipped with both high and low set points which you can test using a millimeter.

    Fan limit switches are relatively inexpensive and simple to replace, yet professional repairs should always be considered when your furnace continues to have issues. Furnaces contain flammable gas, as well as high voltage electricity current, making any attempted repair dangerous without proper training and knowledge of what you are doing.

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    1 comment

    1. Thank you for sharing po such a helpful blog