Why Did My Car Inverter Suddenly Stop Working?

angry kids no power in car
If your inverter suddenly stops working when you're already on a long road trip, you can bet that the kids won't be happy. Fuse / Getty Images

Inverters, like most electronics, typically have two states: working perfectly fine, and suddenly not working anymore. Some internal component fails, for whatever reason, and then nothing happens when you plug it in. So the bad news is that if your car power inverter suddenly stopped working, there’s a pretty good chance that it’s just broken, and it will probably be more cost effective to just buy a new one. The good news is that there are a few things you can check before you throw in the towel.

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 the very first things you’ll want to do, if you haven’t done so already, is to verify that the connection between the inverter and the electrical system, or auxiliary battery, is solid and that the electrical system is in good working order.

  • For cigarette lighter inverters:
  1. Check the socket for obstructions.
  2. Check the socket for potential shorts like paper clips or small coins.
  3. If the socket is clear, plug another device into test it.
  • For battery-wired inverters:
  1. Check for power and ground at the inverter.
  2. If the inverter doesn’t have power or ground:
    1. Check the power and ground wires for corrosion and shorts.
    2. 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 will give a warning, either via an indicator light or warning tone, if the input voltage is too low, but that may not be the case with your particular unit. Of course, if your battery is on the way out, or your alternator isn’t charging properly, those are definitely things you’ll want to get taken care of before you head off on a road trip anyway.

Was the Inverter Used With a High Amperage Device?

Every inverter is rated to provide a specific level of wattage constantly and a different level in short bursts. So if your inverter is only rated to power consumer electronics devices like laptops, handheld game systems, and cell phone chargers, but someone plugged in a hair dryer or a portable fridge, the inverter may have been over-stressed.

Some inverters include built-in fuses or circuit breakers that will pop if that happens, in which case you will need to give your 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’ll want to make sure and stay below the wattage rating of the unit.

In other cases, an inverter may be permanently damaged by plugging in a particularly heavy load, or a device like a fridge that draws a huge amount of amperage when the compressor kicks in. If your inverter was damaged in this way, it may be possible to repair by replacing whatever internal components failed, but simply replacing the unit is probably going to be a better idea.

Was the Inverter Connected Backwards?

If you have a small cigarette lighter inverter, then connecting it is pretty much 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 your inverter up backward, you can look for a built-in fuse or circuit breaker to replace or reset, but there’s a pretty good chance that the unit has suffered irreparable damage if it no longer works.

Replacing an Inverter That Stopped Working

Although you may find that your inverter stopped working due to a blown fuse, corroded power cables, or another relatively simple problem, you will probably have to replace your unit if it stopped working due to an internal fault or improper use. In that case, you’ll want to make sure that you find a replacement inverter that will meet the needs of your specific application. For instance, if your needs are relatively light, and your inverter failed due to someone hooking it up wrong, you may want to consider buying a cigarette lighter inverter. These units are incapable of handling high wattage loads, but it’s also impossible to hook them up backward.

If your power needs are more intense than a cigarette lighter inverter can handle, then there’s a relatively simple equation you can use to determine how large your inverter should be. Of course, installing your new inverter properly will also ensure that it provides you with years of trouble-free service.