Why your Inverter may Keep Blowing Fuses

While some inverters can work reliably for many years, never once requiring any repairs, you cannot rule out the odd and frustrating experience you can experience with an inverter – one where each new fuse you fuse keeps blowing!

What causes this? How do you go about fixing it?

Read on for the likely reasons why your inverter fuse may keep blowing and how you can fix it safely.

Why Does an Inverter Keep Blowing Fuses?

If the inverter fuse blows, it may be because of one of the following reasons:

1. Accidentally reversing the inverter battery’s positive and negative cables. Did the fuse pop when you were connecting the battery cables to the battery posts?

Was the inverter working well before they were disconnected? If so, there’s a good chance that you’ve mistakenly interchanged the cables.

Double-check that the red positive battery cable is connected to the positive battery post and the negative battery cable to the negative battery post.

It happens more often than people realize!

2. There’s been an accidental short at the output of the inverter. The inverter fuse may pop too when there’s a short at the output of the inverter terminals such as when there is a fault such as a short in the appliance plugged into the inverter.

3. The inverter just fails. In some cases, the blowing of the fuse has nothing to do with a fault in the connected appliances, or even wiring.

One or more internal components fail because they are low-quality parts, or from overheating.

This can be explained when an inverter that has previously been working faultlessly starts blowing a fuse even when there has been no change in the wiring or the connected appliances!

Signs that an Inverter Fuse has Blown

The unmistakable sign is there’ll be no power from the inverter but before you associate any loss of power to a blown fuse which may be caused by a low battery voltage, or loose or broken cable connection, you may notice these additional signs:

  • Inverter fuse “popping” sound. If you’re close to the inverter, you may be able to hear the soft pop sound as the fuse blows which is then followed by all connected appliances losing power.
  • On some inverters, there’ll be an inverter overload fault or inverter fault alarm – in some cases as red Led or continuous beep when the inverter is connected to the battery with no output power from the inverter through!

Note, these signs are not confirmation that the fuse has blown.

Additional tests may have to be done to confirm the actual cause of the fault.

What to Do?

Note: Inverters can hold dangerously high voltages for several hours. Follow the safety recommended by the manufacturer.

Once you’ve confirmed that it’s indeed a blown internal fuse before you plug a replacement fuse into the inverter, the priority should be to establish the underlying reasons for the fuse blow. Identify this fist and fix it before you fit a replacement.

here are some suggestions that can help you locate the fault faster

  • Check for a noticeable burn smell. If indeed there’s, use this to narrow down the likely location of the short which could be the inverter cabling – DC and AC, or a within the appliance.
  • Are the cables from the battery to the inverter intact or damaged? Do they show any burn marks or damaged insulation that may have caused the short?
  • Is the power cable supplying AC power to the appliances intact or are there signs of damage such as burn marks on the insulation, or kinks in the cabling? Inspect the cable length for any possible damage and potential areas of shorting. If there is damaged cabling, replace it with the recommended type and gauge as recommended by the manufacturer.
  • Could there be a short in one of the connected appliances? Disconnect the suspected shorting appliance.

Once you’ve fixed the likely cause of the fuse blow, only then should you proceed to replace the fuse.

1. First, disconnect or unplug the cables supplying power to the appliances from the inverter.

2. Then switch ON the inverter. If the inverter powers on with no fuse blow, proceed to reconnect the cablings supplying AC to the appliances ( all appliances should be disconnected).

Does the fuse blow? If not, plug in the appliances one at a time checking for the fuse to blow each time.

3. If the inverter blows the fuse again, then quite likely there is a faulty component in the inverter and you need the services of a qualified technician.

Related Topics

Why an Inverter Keeps Blowing Fuses

If an inverter fuse keeps blowing, it’s usually one of two conditions.

Either, there’s an internal short that’s yet to be fixed or the fuse size (amps) that’s been fitted is a lower rating than recommended or the wrong type.

1. Internal short in inverter

One or more internal components, perhaps a MOSFET, capacitor, or other can short. Until all shorting components are identified and fixed, the replacement fuse will keep blowing.

When there’s an internal short, the fuse blows immediately after the power inverter is switched on. Contact an authorized inverter technician.

2. The undersized or wrong type of fuse

If the fuse fitted is of a lower amperage than recommended or the wrong type – fast blow yet the recommended one should be a slow blow then the fuse will keep blowing too.

In this case, the fuse blow may be intermittent, blowing sometimes only and usually after a delay.

Tips to Change an Inverter Fuse (Safely)

Warning: Always follow the recommended safety guidelines by the manufacturer. Disconnect the inverter from the battery.

Some components in an inverter can retain high voltages for several hours.

Depending on the design of the inverter, the fuses may be easily accessed on the inverter case or on the inside of the inverter requiring that you remove the inverter case to replace the fuses.

Check which of these applies to your inverter model.

Only replace the blown fuse with another of the same rating (amps) and type as recommended by the manufacturer.

Closing Thoughts

If the inverter fuse keeps blowing then there’s an underlying fault that has not yet been fixed.

The common reasons why an inverter fuse may blow include interchanging the inverter battery cable connections, a short-circuit in the cabling supplying power to the appliances on the AC side, a faulty and shorting appliance, or a short in the inverter.

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