Why an Inverter Keeps 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 an inverter’s internal fuse keeps blowing, it may be because of the following reasons:

1. There’s a short at the output of the inverter. This may be in the cabling connected to the inverter output terminals leading to the appliances. Check for any kinks in the cabling or even chaffing along the cable insulation.

2. You may have accidentally reversed the inverter battery’s positive and negative cables. Confirm that the inverter positive cable is connected t0 the battery positive and the inverter negative cable is connected to the battery negative terminal before replacing the fuse and switching the inverter on again.

Interchanging the inverter battery cables happens more often than people realize!

3. There’s a internal component failure in the inverter or the inverter was Dead on Arrival. Sometimes there is a fault in the inverter that is not your making. You may have received a faulty inverter for instance.

Can an Inverter Fuse Blow for No Reason?

Yes, it is possible for an inverter fuse to blow when there is no external factor per se. Some electrical components fail over time from use of weak materials or wear and tear.

Signs that an Inverter Fuse Is Blown

When an inverter’s internal fuse blows, this is what you can expect to happen:

1. No power at the Inverter Power outlet terminals

There’ll be no power available at the inverter output terminals too. Depending on the inverter model, you may also have a “fuse blown LED”, “a fault alarm” or a continuous beep from the inverter when it is connected to a battery.

2. Popping Sound

When an internal inverter fuse blows, there’s usually a popping sound. To hear it though, you’ll need to be next to the inverter.

3. Burnt smell

You may also be able to pickup a burnt smell when next to the inverter.

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 When an Inverter Fuse Blows?

Note: Do not hesistate to contact a qualified electrician. Inverters can hold dangerously high voltages that can injure or kill.

Therefore only proceed to troubleshoot the underlying fault is you are qualified and follow the manufacturer recommended safety precautions.

Step 1. Disconnect the inverter from the battery supply – the inverter should have a battery disconnect switch. Make sure the appliances are also disconnected from the inverter output terminals.

Step 2. Next, try to locate the likely fault. There are usually 2 possible areas – an internal inverter fault or a fault in the cabling connecting the inverter output terminals to the appliances.

To narrow down the fault area faster, use the tips below as a guide:

  • Check for a 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? This may point to a fault in the cabling.
  • 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.
  • It is also possible that there is an internal short in the inverter – the inverter has failed.

Step 3: Fix the likely cause of the fuse blow.

Step 4: Proceed to replace the fuse once you’ve fixed the likely cause of the fuse blow. Make sure you replace the blown fuse with the type and rating recommended by the manufacturer to avoid the risk of electric shock or fire.

Where to Find an Inverter Fuse

Inverter fuse location

Depending on the inverter model, the fuse may be internal in which case you’ll need to open the inverter casing. On some inverter models, the fuse may be located n the outside of the inverter.

Check your inverter’s documentation to see where the fuse is located.

Step 5: Testing the inverter after replacing 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.

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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