Common Problems With Home Heating Furnaces

Gas Furnaces

A standard gas furnace is usually designed to burn natural gas, or methane, to create heat. They can also be modified to use liquefied petroleum (LP) gas such as propane, butane or a combination of the two.

Gas-fired furnaces are the most common type, with propane being more popular in rural areas and natural gas more common in urban and heavily populated areas. Propane is typically liquefied and is easy to store in your backyard until it’s needed to fuel your furnace. Natural gas, on the other hand, is piped directly into your home via a piping network, where it stays in its gaseous form the entire time.

When it comes to comparing natural gas and propane, realize that they produce very similar heat outputs. If you’re trying to decide between the two, it usually comes down to a matter of price, availability and simple personal preference. Of course, if you happen to live in an area without access to a natural gas pipeline, LP will be your sole option.

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Fuel Oil Furnaces

These are declining in popularity because of the high cost of oil. It burns at a hotter temperature than gas does, and it needs a special type of burner to convert the oil into a mist, both of which mean the oil furnace is a completely different design from the gas furnace.

Typically, it’s constructed out of much heavier steel and is built to handle a different kind of flame that acts more like a blow-torch. Because of these heavy differences, oil furnaces are often much more expensive than their gas counterparts.

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Electric Furnaces

This type of furnaces essentially operates like a much larger version of your average toaster. It uses wire coils to heat up the surrounding air. It’s extremely efficient, since none of the heat gets lost up a chimney. However, electrical energy is expensive, so these furnaces can also be a bit pricey.

If you’re concerned about price, some utility companies may offer an option for “off-peak” usage, meaning that they can turn your heat off during the peak season. This can certainly save money, but it also has the potential to leave you with no heat source during some very cold periods. If you’re considering this, it’s best to have a backup heat source just in case.

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Heat Pumps

While not strictly a furnace, this is an alternate way to heat your home. A heat pump operates by pumping warm air from one place to another, effectively heating or cooling a controlled area. In the winter, it extracts heat from the air outside and pumps it into your home. In the summer, it pumps the heat out of your home and back outside, leaving your home much cooler.

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The Furnace Won’t Heat or Won’t Produce Enough Heat

Here’s a question no one wants to answer in the middle of winter: “Why is my furnace not blowing hot air?” You come downstairs on a cold winter morning and try to turn on the furnace, only to realize that the furnace won’t heat up. It’s on, and everything seems to be in order, but it just won’t produce any heat. Or maybe it’s producing a tiny amount, but not nearly what it should be producing.

If your furnace is still producing a tiny amount of heat, run through this list of what to check if a furnace isn’t working:

• Be sure that nothing is blocking the flow of warm air. It could be that the heat is trying to come out but is trapped and can’t find its way out into the open.
• Check that the thermostat is correctly on the “heat” setting and the fan is correctly placed on either “on” or “auto.” If this is correct, turn the heat up by about five degrees and wait to see if anything changes.
• Check all the heating registers in the room, and make sure they’re open. It could just be that they were accidentally left closed, and the heat has nowhere to come out of.
• Take a look at the filter. If it’s dirty, it could be blocking the airflow, not to mention reducing your efficiency. If it looks dirty, replace it right away.
• If none of these steps seem to be making any difference, call a heating and cooling service and ask for a technician to come take a look at it. Most likely, the problem is something more technical and requires an expert’s attention.

If your furnace turns on but won’t produce any heat at all, try these fixes:

• Make sure the thermostat is set to “heat.” If your thermostat has a cooling option, it could be a simple matter of needing to be switched to heat.
• The ambient air might not be cold enough for your furnace’s current setting. Try turning the thermostat up to see if it kicks on in response to the higher setting.
• Look at your circuit breaker. Make sure that the furnace’s circuit breaker is switched on and that it hasn’t been blown. You may need to check both the main electrical panel and any subpanels that also power the unit. Try flipping the switch on and then off again. If the fuse is blown, and it’s beyond one of these easy fixes, you may need to call an electrical service to get it repaired.
• Make sure that the furnace’s power switch is turned on. If you’re having trouble finding the switch, look next to or inside of the furnace cabinet.
• If you have a gas furnace, the gas valve may have been shut off, or the pilot light may have gone out. To fix this, check your furnace’s ignition.
• Make sure your thermostat itself isn’t faulty.

If these strategies fail and you’re still getting no hot air from the furnace, it may be time to reset the unit. If you’re wondering how to reset your furnace, know there are several ways depending on the type and age of your furnace. If your furnace is more modern, it likely has no pilot light but does have a button you can push that will take care of the whole process. If you have a furnace with a pilot light, you will need to perform a few extra steps:

• Switch the furnace and breaker off.
• Open the access panel and turn off the gas control valve, letting the gas dissipate for at least five minutes.
• Turn the gas back on, turn the switch to “pilot,” then quickly light the pilot using a long barbecue-style lighter. If it does not stay lit, you may have a clogged filter, an issue with the gas line or another issue that requires a service call to repair safely.

When a reset doesn’t fix the issue, it’s time to call up the professionals. Let them know your furnace isn’t working and provide the relevant details that will help pinpoint the problem.

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The Blower Is Continuously Running

If the blower on your furnace won’t stop running, the problem could be one of two things. It could either be a problem with the room thermostat or the limit switch.

Look at your thermostat to see if the fan is set to “on.” If so, set it to “off” or “auto.” If you change this setting, however, you’ll also have to adjust the limit switch.

The limit switch is usually located on the furnace directly below the plenum, which is the box that distributes the hot air into all the ducts and vents. Its job is to shut the furnace off if the air in the plenum becomes too hot.

Carefully follow your unit’s instructions to adjust the limit switch, or call a technician if you don’t feel comfortable doing it yourself. In most cases, the lower pointer will need to be set at about 90 degrees, and the upper pointer should be at roughly 115 degrees.

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The Thermostat Is Malfunctioning

This could take on several different forms. A malfunctioning thermostat could result in a blank readout, inaccurate readings or even in your furnace continually running. Since this problem can have so many varied faces, it’s difficult to project an exact situation.

Our best advice for this program is to make sure that everything is switched on and is on the correct settings. Refer heavily to your user’s manual, and if things get beyond your capacity to understand and fix, don’t hesitate to call in a professional.

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There Is a Problem With the Electrical Ignition or Pilot Light

Your furnace’s ignition could very possibly be malfunctioning and causing problems that could lead to intermittent levels of heat or no heat at all.

Pilot lights are more common on older gas furnaces, while newer furnaces typically use an electronic ignition. If the pilot light on your older furnace won’t remain lit, there could be a couple of things wrong. The flame could be set too low, the cutoff valve might be defective, the pilot orifice might be clogged or the thermocouple might be broken.

If the thermocouple is the problem, this will require a professional. A clogged pilot orifice, however, can be cleared with a small piece of wire, although you must be sure to switch off the gas before doing this. If the pilot’s flame has been set too low, simply turn it up slightly. Check your manual to see exactly where it should be set.

If there seems to be a problem with the ignition, try switching it on and then off again. Listen for the sound of a spark catching, or watch for a glow. If this doesn’t work, clean the flame sensor with a piece of Emory paper.

If none of these items fix the problem, call in a professional right away.

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The Filter Is Dirty

This is an easy problem to diagnose and frequently contributes to a gas heating system not working properly. You will usually be able to see for yourself that the filter is dirty. A dirty filter can cause all kinds of problems in your furnace, from causing it to cycle on and off too often, provide only a small amount of heat or not work at all.

To fix this problem, either clean the filter or replace it entirely if it’s dirty beyond repair. Make a note on your schedule to clean the filter regularly, as this is one of the easiest ways to prevent common furnace problems.

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The Furnace Cycles Too Frequently

Your furnace keeps cycling on and off with a breakneck frequency, not staying on long enough to truly heat the house. What do you do?

The odds are good that this is a problem with your thermostat. If your model is equipped with a small lever that moves along a calibrated scale that marks the cycle lengths, try adjusting this. Just make sure you don’t accidentally reset the heat temperature. To change this setting, move the lever down the calibrated scale by one mark. Give the thermostat a few hours to adjust to the new setting and see if this fixes the problem.

You can also try cleaning or replacing your filter if it appears to be dirty. If this doesn’t work, you may need to replace your thermostat.

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The Furnace Won't Turn On

One of the most frustrating scenarios you can have with a furnace is when it won’t turn on at all. A furnace not turning on can have several causes that may vary in complexity. What causes a furnace not to kick on? If your furnace isn’t responding when you switch it on, try these troubleshooting strategies:

• Inspect the system’s power cord to ensure it is not damaged in any way.
• Check the heating system’s control board to see if it has any burn marks that would indicate an electrical short.
• Check the inspection window in the blower compartment. The light there should flash green. If the light is red or not flashing at all, there may be an issue with the motor, control board, run capacitor or transformer that will need professional attention.
• Check the condensate reservoir. If it’s full, the system won’t turn on, so empty the reservoir and make sure the pipe is not blocked. If blocked, the pump may lose power and have to be replaced.
• If you can’t get the pilot light to light or stay lit, the issue may be a dirty assembly or sensor.
• If your home’s gas supply is interrupted, your gas furnace won’t have any fuel.

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Vacuum the Blower

At least once a year, you should make an effort to vacuum out the area surrounding your furnace’s blower. While you’re already cleaning, it’s also a good idea to slide out the fan unit and clean each of the blades carefully with a toothbrush.

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Clean and Replace the Filters

As we mentioned, having dirty filters can get you in a lot of trouble. To avoid this, check your filters at least once a month. Clean them if they’re dirty, and replace them if they’re so dirty that they’re past cleaning.

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Check the Batteries

When a thermostat begins malfunctioning, it could be something as simple as a few dead batteries. To prevent this, test your batteries regularly and replace them whenever they begin to show signs of age or stop functioning altogether.

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