How Do You Know If Your Furnace Fuse Is Blown?


Sinclaire Enterprises, Inc.

140 South St., Walpole, MA 02081
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It’s one of the last things anyone wants to happen during the Massachusetts winter: your furnace stops working. Even in the best-case scenarios, you’re looking at some discomfort and inconvenience, possibly for several hours. If your furnace stops working during a major storm, the situation could be much more severe.

Fortunately, one of the most common causes of a furnace not working is also typically one of the easiest to fix. That’s when the furnace fuse is blown, or the circuit breaker has tripped.

When it’s the circuit breaker, you must go to the panel and flip the switch back on. For a blown furnace fuse, relief could be just minutes away if you have a spare fuse. If you don’t, a quick trip to the store to get a replacement fuse might be the extent of the inconvenience you experience.

Note: If the circuit breaker keeps tripping or fuses repeatedly blow, you have a more serious problem that requires professional attention. For Newton Furnace Repair or elsewhere in the Boston area, you’ll find fast and effective relief with Sinclaire Home Services, a fully licensed and insured HVAC service with decades of proven reliability.

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What Causes a Furnace Fuse to Blow?

You’re probably already familiar with blown fuses and replacing them if you own a car. From time to time, fuses blow, and usually, replacing them is all you have to do. It’s the same with a furnace fuse. Here are some things that can cause them to blow:

  • Dirt and Dust. You probably don’t enjoy replacing the air filters in your home, which you typically should do once a month, but it’s essential. When dirt and dust clog air filters, particles can end up in places in the heating system where they can cause problems. For example, dirt in the blower motor can act like sand or grit in gears. Overheating and excessive strain can result, leading to an electrical overload that can cause the system to shut down.
  • Wiring Issues. Loose, bad, or damaged wiring can cause a fuse to blow and might be the culprit if a fuse is repeatedly blowing. If you are going to inspect the wiring and possibly tighten connections or replace faulty strips, there are a couple of important things to know. First, you must always cut off power to the unit beforehand to protect yourself from electrical shock; do this by turning the circuit breaker to the off position. The other is that unless you know what you’re doing, you could worsen the problem. When there is a wiring problem, it’s best to call a professional electrician or HVAC technician.
  • Wear and Tear On Parts. Just as parts in a car are more likely to malfunction, break, or perform inefficiently as they age, components in a heating system will wear out the older they get. Unusual noises coming from the furnace often indicate faulty parts. Determining which parts aren’t working correctly and why can be difficult and is best left to a professional HVAC technician. If you find yourself facing repairs more frequently for an older system, it’s probably a better long-term decision to replace the system with a newer one.
  • A System Not Up To The Job. Sometimes the heating system needs to be bigger or more powerful to heat the area you want. For example, this could result from an inexperienced HVAC technician installing the wrong unit or from keeping the old system after a home expansion. When the system isn’t up to the demand, it works longer and harder, building up to an electrical overload and failure.
  • Metal Frame Around The Thermostat. Metal frames around thermostats are known causes of blown fuses. The wiring inside the thermostat comes into contact with the frame, causing voltage issues. This situation is almost always a problem for a professional to handle.

What Makes a Fuse Blow Repeatedly?

We already mentioned that if this is happening, you should contact a pro HVAC service, but here are some of the things that can make a fuse keep blowing:

  • Excessive Strain. As mentioned above, sometimes a heating system isn’t cut out for what you need it for in your home. This can be because the unit is inadequate for the space or because it isn’t getting enough power. Either way, the fuse can keep blowing because the unit can’t handle the demand.
  • Clogged Filters. See above. This situation you can fix on your own if the blower motor hasn’t been damaged.
  • Insufficient Wattage in The Fuse. If you accidentally use a fuse with insufficient wattage for the unit, it will keep blowing. This, too, you can fix on your own.
  • Faulty Parts. See above.
  • Contact With Water. This is unlikely but still possible. If the furnace has consistent contact with a water source, that will cause shorts.

The bottom line is that if a fuse keeps blowing and you know you have the right wattage and the filters are clean, you have a serious problem that needs professional attention.

How To Tell If the Furnace Fuse Is Blown

This is pretty easy. First, check the circuit breaker panel to see if the one for your furnace flipped. If it hasn’t, cut the power off so you can check the fuse.

Furnaces with fuses usually have them in the control box with the blower. Remove the fuse and inspect it. If you’ve ever replaced a blown fuse in a car, you know what to look for here. If you haven’t, look for broken wiring, discoloration, or cloudiness.

Replace the blown fuse with a new one of the right size and wattage. Make sure your hands are completely dry, and then switch the circuit breaker back on. If the furnace comes back on and the fuse doesn’t blow, you probably fixed the problem!

Professional Furnace Maintenance, Installation, and Repair

For Newton furnace repair, a furnace repair in Franklin, or furnace servicing anywhere else in the Boston region, you can trust Sinclaire Home Services. With more than 70 years of serving Boston-area families and businesses, we built an unmatched reputation for quality and reliability.

Do you need a furnace repair, installation, or routine maintenance? Contact Sinclaire Home Services today!