Your car’s battery stores a lot of electricity and the high amperage levels required to cold start an engine can be dangerous if they’re allowed to leave the battery in an uncontrolled fashion.
When your battery is in good shape and there are no issues with the way it’s hooked up, the various transformers, regulators, and other components ensure that each system receives the right amount of power for its duties. But sometimes, malfunctions can happen and cause a direct discharge of battery power that can result in a whole lot of not-so-fun scenarios that can involve fires, melting, and repair bills totalling into the thousands.
How about the melted headlight housing on this SUV? This post on Reddit’s r/JustRolledIntotheShop shows us what happens when you’re not careful jump-starting a dead battery. If you connect the booster cables incorrectly, you might just get a short circuit that puts on a cool fireworks display and melts your booster cables (and anything they’re touching) in the process.
This SUV’s thermal incident will cost it a new headlight housing, maybe thousands of dollars in repairs, and the replacement of electronic components that have been fried. Finding replacement computers and modules during a global microchip shortage won’t be much fun.
Reddit user ajsobie says similar results can come from boosting a car with a short circuit, even if the cables are hooked up correctly.
“Cables can be connected correctly and still start a fire,” he says. “Happened to me once. Eventually found that the alternator in dead car was fried and shorted. Cables caught fire about 30 seconds after starting my truck. Saw it out of the corner of my eye and launched those suckers immediately. My radio didn’t work after that, but otherwise no detectable electrical damage to my truck. Slight burn to my flared fender where the cable made contact.”
Lesson Learned: If you’ve giving or receiving a boost, be sure the other car is healthy and be positive you’re hooking up the jumper cables properly.
Here’s another fate-tempting example of a serious problem waiting to happen.
In this post, u/jcat47 shows us a customer-created fix for an engine control unit that kept blowing fuses. Fuses are sacrificial safeguards built into electrical stuff, basically a cheap electrical connector that blows or melts if power flowing through it exceeds a safe limit. If a component keeps blowing its fuse, it needs to be checked professionally for potentially serious wiring trouble.
But some owners choose to bypass their fuses, perhaps using a different fuse with a higher-than-safe rating, or simply connecting the fuse blades with some metal wire so that power continues to flow even after the fuse blows. This can cause extensive damage to expensive components of the vehicle, and is also a fire risk and a spectacularly bad idea.
Here’s another example of what can happen when you incorrectly modify your vehicle’s wiring and fuses. In this case, a non-fused wire began to melt though a nearby cable under the vehicle’s hood, burning through its insulation. Had that been a fuel line, a fire would have been inevitable.
Consider this example that illustrates a number of fuses that blew when the owner of this Toyota Highlander Hybrid incorrectly installed a new battery. This resulted in an unchecked flow of power from the battery, which blew several fuses – including the 120-amp DC/DC fuse used by the vehicle’s hybrid system.
A labor-intensive repair ensued, though thankfully, the fuses were the only damage – and once replaced, the vehicle ran just fine.
Still, as u/SR2K concludes “be glad that the $10 of copper protected the $3,000 worth of computer modules that would have been fried if it weren’t for engineers planning for people to be idiots.”
Lesson Learned: If you’re boosting your car, be sure you’re hooking things up correctly. If you drive a modern car, leave battery replacements to an expert to avoid potential surprises, catastrophes, and electrical system fireworks. If you’re adding an aftermarket stereo or other electronic equipment to your ride, consider professional installation to avoid electrical gremlins, fires, system damage, and other hazards that aren’t covered by warranty.