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So I told this little story to the dealership service department, and they were baffled. Never heard of anything like it in ten years, said they'd have to examine it very closely.

Here's what happened two months ago:

I drive a Subaru Legacy 97. I turned the car on and was about to shift out of Park to drive away, so I stepped on the brake and as I did so, my headlights dimmed, my radio volume shrank and all the interior displays hiccuped. I took my hand off the shift, all thoughts of driving forgotten, and started playing with the brake. It did the same thing repeatedly. After a few tries, I stomped on the brake and everything blinked off entirely for a second, and the engine nearly shut down.

The electricity came back in less than half a second -- it wasn't a prolonged outage -- just a brief interruption -- so the engine caught itself and stayed running. But for just a moment, the whole car had shut off.

This only happened once to that extent once, and I have been unable to reproduce it. Sometimes, however, braking does ever so slightly dim my interior displays, so there is a definite consistency to this.

Since the dealership had no idea, I thought I'd try tapping the infinite well of experience that is Mechanics.SE. Any thoughts?

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  • I had this same problem right after I had both of the front brake rotors and calipers replaced. I was driving 20mph in heavy traffic and every time I would press on the brakes and come to a full stop my dashboard would get little spurts of electricity causing the rpm to go from 0 to 1000 intermittently. It didn't seem like it was having any effect on how the engine was running however. I pulled over after I started smelling a bit of burning plastic and then my car wouldn't restart.
    – user6911
    Sep 6, 2014 at 21:33
  • does your issue happen only when braking while stopped or is it all the time because I think a weak engine or a bad sensor can make the engine want to stall because the brake booster is robbing it of its power
    – method
    Sep 12, 2016 at 4:52

1 Answer 1

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Sure enough, you've got a damaged wire that is shorting out the entire electrical system. So think about what happens when you press on the brake pedal, it sends power to your brake lights at the back of the car, so if one of those wires were shorting, you would only notice it when you tap the brakes.

The weird thing is, this doesn't happen very often, because that's what fuses are for. Your brake light fuse should blow when your brake lights short out, preventing the problem from spreading to the rest of your car and killing your engine. So some how the problem seems to be bypassing a fuse. You should check your fuses.

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  • yep - I can't understand why the fuse doesn't go, but this seems like the only likely cause...
    – Rory Alsop
    Feb 5, 2013 at 9:53
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    Fuses don't blow on quick faults. I've even had a fuse (and part of the wiring harness) melt during a rapidly occuring intermittant fault. It was ugly. Fix this ASAP before you have to start pulling and repairing/replacing wiring harness.
    – Brian Knoblauch
    Feb 5, 2013 at 15:26

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