If you’re a homeowner in San Marcos, CA, whose HVAC suddenly quit working, it’s easy to assume the worst. After all, HVAC systems aren’t cheap, and neither are complex repairs. However, what you may not realize is that one of the most common reasons for sudden HVAC failures is blown fuses. Although you may not realize it, HVAC systems contain fuses that protect them against overvoltage. This prevents damage to your HVAC and can save you a fortune in repair costs if your home experiences a power surge. So, your HVAC fuse is one of the first things you should check if your system stops functioning. Here’s how you can tell if your HVAC fuse is blown.

What Kind of Fuses Do HVAC Systems Use?

Modern HVAC systems typically use TR fuses to guard their compressors against power surges. The idea is for the fuse to burn out before the compressor can. That’s an excellent tradeoff when you consider that a new compressor could cost you anywhere from $400 to $1200, depending on the type of HVAC you own. By contrast, replacing an HVAC fuse costs an average of $75. Most HVAC systems also have a fuse that protects their control circuitry. Those are typically blade-type or glass fuses that you’ll find mounted on a circuit board inside your HVAC’s indoor unit.

Symptoms of a Blown HVAC Fuse

There are a variety of symptoms that might indicate a blown HVAC fuse. In the case of the compressor’s TR fuse, the most common symptom will be that your outdoor HVAC unit stops functioning. At the same time, the indoor unit will likely keep working and may continue cycling its blower fan on and off in response to your home’s thermostat.

You may also notice a slight burning smell if your HVAC’s TR fuse has burnt out. The smell should not be overwhelming and should dissipate within minutes of the fuse blowing. If you notice a persistent burning smell, you should immediately head to your home’s electrical panel and turn off the circuit that powers your HVAC. Then, you should call Oak Island Heating and Air Conditioning for immediate assistance. A strong burning smell could indicate an electrical fire or a larger component failure inside your outdoor HVAC unit.

In some cases, you may hear a slight occasional buzzing sound coming from your outdoor HVAC unit if its fuse has blown. This indicates that your HVAC control board is still signaling the compressor to turn on and that it’s unable to do so. On the other hand, if it’s your HVAC control board fuse that’s blown, you would see totally different symptoms. Your thermostat may shut off if it’s the type that draws power from your HVAC itself. Or, your HVAC might stop responding to your thermostat, refusing to provide heating, cooling, or both.

How To Check for a Blown HVAC Fuse

There are a few ways that you can test your HVAC fuse yourself to see if it needs replacement. However, this isn’t something you should attempt unless you’re familiar with electrical wiring and how to use a multimeter. If you’re not, it’s a much better idea to call Oak Island Heating and Air Conditioning for help. Since there are high voltages involved, there’s a risk of electrocution if you don’t test the fuse in the right way.

If you own a multimeter and feel confident in doing so, it’s rather easy to test your HVAC fuse. Begin by turning off the circuit that powers your HVAC system. Then, you must locate the fuse. If you’re aiming to test the TR fuse, you’ll find it in one of two places. It will either be inside the outdoor unit’s power disconnect box or behind a panel on the outdoor unit itself. Once you’ve located it, you’ll need your multimeter.

To test the fuse, set your multimeter to the continuity test setting. Then, touch the probes to either side of the fuse. If the fuse is OK, the multimeter should beep or indicate that you’ve completed the circuit. If you get no such indication, that means the fuse is bad and must be replaced. You can perform the same test on the control board fuse, too. In that case, however, you might need to remove the fuse from its holder to access its contacts and perform the test.

It is also possible to test a TR fuse by using your multimeter to test the voltage passing through it with the power on. However, this isn’t something you should ever try to do on your own. With the power turned on, this is a risky test that you should leave to a professional HVAC technician.

Why Would Your HVAC Fuse Blow?

If you discover that a blown HVAC fuse is the reason for your HVAC problem, the next step is figuring out why it happened. If it was the result of a momentary power surge, all you should need to do is replace the fuse to restore your HVAC to working order. If you put in a new fuse and it blows again, it means your HVAC has a different problem. The following are some of the common causes of persistent HVAC fuse failures.

A Circuit Malfunction

If your HVAC fuse keeps failing, it could be a sign that there’s too much incoming voltage coming from your home’s electrical panel. That could indicate a problem with a circuit breaker or another systemic issue in your home’s wiring.

Loose Electrical Connections

If any of your HVAC’s electrical wiring has come loose, it could lead to a short circuit that will blow your HVAC fuse again and again. The loose connections can be anywhere along the circuit, from the wiring coming from your home’s electrical panel to inside your outdoor HVAC unit.

A Faulty Capacitor

When your outdoor HVAC unit turns on, it draws a huge amount of power to get its fan started. Modern HVAC systems contain capacitors that store energy to provide a boost to help minimize the power drain from your home’s electrical system. If that capacitor fails, it could cause your HVAC fuse to blow.

Malfunctioning Fans or Compressor

Malfunctions in your HVAC compressor or fans can also lead to blown HVAC fuses. The compressor and fan in your outdoor unit could lead to a blown TR fuse, and the blower fan in your indoor unit could lead to a blown control board fuse.

Your Trusted HVAC Repair Experts

Whether your HVAC has a blown fuse or is suffering from some other issue, Oak Island Heating and Air Conditioning is the place to turn for help in San Marcos. We offer HVAC installation, repair, and maintenance services, as well as smart thermostats and indoor air quality services. We have over 70 years of combined HVAC industry experience on staff and have been a part of the local community for over 20 years. Plus, we’re Better Business Bureau accredited with an A+ rating, so you can trust us to deliver quality workmanship, fair prices, and excellent customer service at all times. So, if you think you’re dealing with a blown HVAC fuse or any other HVAC problem in San Marcos, call our experts at Oak Island Heating and Air Conditioning today.

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