Reasons a Car Power Inverter Might Suddenly Stop Working

Check known causes before replacing it

Inverters, like most electronics, typically have two states: working perfectly and suddenly not working at all. Some internal components fail, for whatever reason, and nothing happens when you plug it in.

The bad news is that if your car's power inverter suddenly stops working, there's a chance it's broken. In this case, it will be more cost-effective to buy a new one than to troubleshoot the broken one you have. The good news is that you can check a few things before you throw in the towel.

Kids using headphones and laptop in car

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Does the Inverter Have Power?

Since inverters work by massaging a 12V DC input voltage into 120V AC, it stands to reason that your inverter won't work if it doesn't have a good connection to your vehicle's electrical system. So, verify that the connection between the inverter and the electrical system, or auxiliary battery if you have one, is solid and that the electrical system is in good working order.

Cigarette Lighter Inverters

If your inverter plugs into the cigarette lighter on the dash or its replacement—a 12v accessory outlet often found in modern cars—a few things can cause the 12v outlet to fail.

  1. Check the socket for obstructions.

  2. Examine the socket for potential shorts caused by metallic items such as paper clips or small coins.

    Don't reach into the socket with any metal object such as a screwdriver or tweezers. You could be shocked.

  3. If the socket is clear, plug another device into it to test it.

Battery-Wired Inverters

If your inverter is wired to the battery:

  1. Check for power and ground at the inverter using a tool made for this purpose.

  2. If the inverter doesn't have power or ground, check the power and ground wires for corrosion or shorts.

  3. Check any in-line fuses or fuse box fuses, if present.

Even if the inverter has power and ground, it may fail to work if the battery and electrical system aren't in good working order. Some inverters give a warning via an indicator light or warning tone when the input voltage is too low, but that may not be the case with your unit. If your battery is on the way out or your alternator isn't charging correctly, take care of those before you head off on a road trip.

Was the Inverter Used With a High Amperage Device?

Every inverter is rated to constantly provide a specific wattage level and a different level in short bursts. If your inverter is rated to power consumer electronics devices like laptops, handheld game systems, and cellphone chargers, but someone plugged in a hairdryer or a portable fridge, the inverter may have been overstressed.

Some inverters include built-in fuses or circuit breakers that pop if that happens, in which case, give the inverter a once-over to look for a reset button or fuse holder. If you find one, resetting the breaker or replacing the fuse may return your inverter to good working order, although you need to stay below the wattage rating of the unit in the future.

In other cases, an inverter may be permanently damaged by plugging in a device such as a refrigerator that draws a huge amount of amperage when the compressor turns on. If the inverter was damaged in this way, it might be possible to repair it by replacing the internal components that failed, but replacing the entire unit is probably a better idea.

Was the Inverter Connected Backward?

If you have a small cigarette lighter inverter or accessory outlet, connecting it is foolproof. You plug it into the cigarette lighter socket, and you're done. However, connecting a battery-wired inverter backward can permanently damage the unit.

If you suspect that someone hooked up your inverter backward, look for a built-in fuse or circuit breaker to replace or reset, but there's a chance that the unit suffered irreparable damage if it no longer works.

Replacing an Inverter That Stopped Working

Even if you discover the inverter stopped working due to a blown fuse, corroded power cable, or another problem, you probably should replace the unit if it stopped working. In that case, look for a replacement inverter that meets the needs of your specific application.

For example, consider buying a cigarette lighter inverter if your needs are relatively light, and your inverter failed because someone hooked it up to the battery incorrectly. These units cannot handle high wattage loads, but it's impossible to hook them up backward.

If your power needs are more intense than a cigarette lighter inverter can handle, use this equation to determine how large the inverter should be. Still, installing your new inverter properly will also ensure that it provides you with years of trouble-free service.

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