Mind Boggling Wiring Diagrams

Dear Car Talk:

Back in the ’60s and ’70s when my friends and I were kids working on our own cars, repair manuals always had the wiring diagrams somewhere toward the back of the book. Even back then, those wiring diagrams took up several pages with complicated drawings that always intimidated us. So we never messed with wiring.

Here’s my question: What in the world do the wiring diagrams look like now? My mind is boggled just imagining it. — Michael

The Oxford English Dictionary might need a word stronger than “boggled” for you, Michael. When we first opened the garage, we used to swap out a lot of VW engines. And when you pulled the engine, there were about five wires you had to detach. And you were done. Now, a typical engine compartment has 500 wires.

If we were talking about hair, it’d be the difference between Patrick Stewart and Martha Stewart.

Just think about the electronics on a modern engine. You’ve got electronic throttle, sensors galore, feedback systems, fuel injectors, safety systems and more. And we’re not even getting into the cabin electronics. There are a number of things that are done by printed circuit board. But there are still plenty of wires in there running from sensors to computers

The good news is, hardly anything goes wrong with automotive wiring anymore. Today’s connectors are all weather-tight, and they’re pretty much designed to operate under water.

It used to be commonplace that wires would get wet, would rust or short out, or their connectors would corrode. But it’s rare these days that anyone has a problem with wiring, unless they crash the car and crimp 40 or 50 wires. And in that case, the biggest issue is finding the problem. You drive into the back of a Ben & Jerry’s truck, and six months later, you have no tail lights and your seat heaters are permanently set to “add grill marks,” and you don’t know why.

By the way, electric cars, believe it or not, have fewer wires. They don’t have any of those sensors needed to keep a gasoline engine running smoothly and cleanly. They still have safety systems, and a computer, but due to the simplicity of an electric motor, they have many fewer wires.

So maybe you want to avoid looking at gasoline-engine wiring diagrams for now, Michael, and wait until we’ve all switch over to electric vehicles before having a look. But still, get permission from your cardiologist first.

Todays Car-o-Scope

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