Why Your Furnace 3 5 Amp Fuse Keeps Blowing – Must Read the Hidden Secrets!

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Have you ever experienced the harrowing experience of discovering your furnace’s 3 5 amp fuse keeps blowing? This is an all too familiar occurrence, particularly if you live in a colder climate or have recently undertaken any remodeling work.

Don’t despair! Here are three simple steps to prevent this from happening again.

What is a Furnace Fuse?

A fuse is a device that’s designed to dissipate excess power; if it blows before the circuit is complete, it will automatically trigger an electrical overload. Typically, this would prevent the entire facility from sustaining damage or even catastrophic consequences!

Furnace fuses are typically located within the control box of your home’s HVAC system. They are utilized to protect against short circuits on their own – which can occur if connected components aren’t installed properly.

How to Replace a Furnace Fuse:

If you have a 3-5 amp fuse blowing, you will need an amp hour meter to identify the issue.

  • Make sure all wires are securely attached to the wall outlet where your furnace is connected. Remove any screws that secure the unit and slowly guide it out of its enclosure until completely free.
  • While holding the circuit breaker in place with one hand and unscrewing the fuse with the other, carefully pull out the fuse from within – do not force anything! If you can hear any tinkling or clicking noises coming from inside the fuse itself then this may signify that it needs replacing.

Fuse and Circuit Board Location for Your Furnace

Through commonly occurring malfunctions and issues, it’s prudent to take a proactive approach to identify the source of any electrical conundrum. In order to achieve this, you could consider employing professional assistance when encountering a heating system malfunction or exhibiting other signs of heat-related trouble; after all – they have access to specialized tools that may expedite resolution!

If your furnace has been unresponsive despite attempting to rectify the situation with fuses, one possibility is likely that its circuit board may require replacement. To locate this component, begin by locating the thermostat located in your HVAC unit.

To locate the circuit board for a furnace, locate the fuse panel mounted on an accessible wall surface.

Fuse and Circuit Board Location for HVAC System

You may not realize it, but the location of your furnace circuit board can affect its longevity.

The fuse is an essential component that safeguards AC power in your HVAC system. It prevents damage should any electrical short occur within the system; thus keeping the running temperature consistent and preventing fires itself is a desirable result!

There are two types of fuse that you might encounter – fixed and time-delay type fuses:

  • Fixed fuses withstand high currents without deforming or melting
  • whereas time-delay provides added protection for longer-lasting systems.

How to Test a Furnace Fuse:

If you’re experiencing an issue with your furnace or air conditioner, you may opt to replace the fuse or simply reset the breaker. However, if troubleshooting fails to reveal the source of the problem – or perhaps even if it doesn’t – you could employ a more rigorous test. Here are some suggestions on how to conduct this phase in order to ascertain if anything is amiss!

Immerse a clove-sized section of wire into one of your circuit’s fuses for three seconds and then retest after 5 minutes. If there has been no change in temperature, then all indications point towards either no damage or damaged wiring; however, if it’s still hot after said amount of time elapsed then that must mean that the wiring within that area has sustained damage. Yikes!

Replacing a Furnace Fuse by Hand:

If your furnace fuse keeps blowing despite making sure all its components are in good working order, you may need to replace it with an identical one. To expedite this process, simply unscrew the existing fuse and insert another accordingly – just as if you were replacing a light bulb!

If you’re attempting to identify which fuse will be compatible with your unit, check out our guide on locating an appropriate replacement.


The most likely cause of your furnace’s fuse blowing is corrosion. To rectify this issue, contact a professional to have them inspect and clean your system. This process can be quite laborious; so if you’re interested in expediting it – let our team handle it!

Don’t take chances when it comes to protecting your family from dangerous gas leaks; call us today for an estimate on repairing or installing a new furnace!