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Top 10 Causes of Furnace Electrical Problems

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Last Updated on March 12, 2019


electric furnace problems

Furnace fuse keeps blowing? This guide to electric furnace troubleshooting explains the common causes and fixes.

If you have been experiencing electric furnace problems (specifically the furnace fuse blows when the heat turns on) throughout the holiday season, you might have assumed the problem is those cheap holiday string lights. But when it happens again (even after Santa has left the building along with the spike in your electric bill), you’re probably wondering what to do now.

If your furnace is blowing a fuse repeatedly, leaving you with no power to the furnace, your first step should be to call in an experienced HVAC repair professional. It’s possible that the problem could turn out to be with your electrical system rather than the furnace itself, but your HVAC system is the most likely suspect, so it makes sense to start there.

Electric furnace problems can be tricky to solve because there are so many possible causes, and also because the problem can be intermittent. If that’s the case, it may require a few tries to get to the bottom of the issue that’s causing the HVAC fuse to blow. The problem could even be related to a thermostat fuse. Pay attention to details so you can provide your technician with as much information as possible. Does the fuse blow when the system starts up or when it’s been running a while?

Make sure your HVAC technician checks all of the following causes when troubleshooting electric furnace problems.

Troubleshooting: top 10 causes of electric furnace problems

1. Clogged filter.

If your furnace’s air filter hasn’t been changed in a while, it may be completely clogged with dust and debris. Eventually all that dust ends up in the blower motor, which can then overheat, causing the fuse to burn out and possibly even catch on fire. The fix is simple in this case: replace the furnace fuse, replace the filter, and have the system thoroughly cleaned.

Learn more: Fall Furnace Maintenance: How to Change Your Furnace’s Air Filter

2. Loose wire.

Over time, the vibration that results from the furnace running can cause internal wires to become loose. Eventually, a wire gets so loose that it causes a short, leaving you with an electric furnace that’s not heating. It may take some time to find the problematic wire, but fixing or replacing the loose wire will take care of this problem. To prevent this problem in the future, make sure you have your system regularly inspected and tuned up, to keep those wires tightened and prevent shorts.

Learn more: 10 Fall Maintenance Tasks That Prevent HVAC Repair

3. Contact with water.

Have there been any water leaks, from the furnace or anywhere nearby? This could happen if your furnace is tucked up in a crawl space somewhere. Check for leaks that could be causing a short.

Learn more: Don’t Let Furnace Water Leaks Ruin Your Holiday

4. Wrong fuse.

Did you allow a less-than-qualified person to try to service your furnace? It’s possible they put in a fuse that was too small to handle the capacity of your heating system. An expert will spot this problem immediately.

5. Dirty fuse.

Again, if you haven’t had your furnace maintained in a few years, the parts may be dirty. When an HVAC fuse gets covered in soot and grime, it may no longer be able to connect sufficiently and can fail.

6. Faulty starting capacitor.

If the capacitor that starts the system is failing, you could get intermittent electrical problems. Replacing the capacitor is an inexpensive fix and will solve the problem.

7. Transformer failure.

If your building’s electrical system supports 120 volts, your furnace needs a transformer to convert to the correct voltage to run the controls, ignition and timers. The electric furnace transformer may be failing, causing the system to short. If so, it will need to be replaced.

8. Bad blower motor.

A failing blower motor can also cause the blown fuse. The strain causes the motor to draw too much power, causing the short. If this is the problem, your technician will need to replace the motor.

9. Failing valve.

If you have a gas furnace, one of the valves may be failing. When a valve is unable to open and close properly, it can sometimes heat up, causing an electrical short that blows a fuse.

10. Electric furnace thermostat control wire.

Your furnace’s control board has a separate fuse that protects it from getting too hot. If someone is poking around your furnace and is not too careful, they could more wires so that they come into contact with the furnace’s wire frame, causing them to short and blow the fuse on the furnace board.


Is your furnace running but blowing cold air? Check out this post: Furnace Blowing Cold Air? 13 Common Causes

The good news and bad news about electric furnace troubleshooting

First the bad news: electric furnace problems can be frustrating. There are so many possible causes that it can be time consuming to discover the correct diagnosis. The good news? You can prevent almost all of these problems by regularly maintaining your HVAC system.

If you’ve been neglecting HVAC preventative maintenance, you may be surprised to find that it’s not as expensive as you thought, and can actually pay for itself in cost savings. Preventative maintenance contracts can be designed to suit the needs of your equipment, your business and your budget.

Find out more from our helpful guide: HVAC Preventative Maintenance Contracts: How to Find the Right One for Your HVAC Infrastructure.

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