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I'm having trouble starting my car. First of all, the battery is empty. All I hear is click click click click.... The battery is relatively new, bought it last fall. I borrowed a jump start kit and that got the car going. It is going very rough when I rev the engine a little bit.

Once I unplug the jump start kit, the fun starts. The electrical system does all kinds of funny stuff. I've recorded a video to show what I mean.

https://youtu.be/Or1qiuQJQTs

The flickering of the lights isn't introduced by the camera, it's actually doing that.

I've left the car running for about 10 minutes. Once I turn it off, I can't turn it back on without the jump start kit.

Anyone got an idea what is going on here?

Edit: The voltage with the engine running is between 14.2V and 15.4V.

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  • Have you used a volt meter to see what the charging system voltage is while the car is running?
    – vini_i
    Commented Feb 1, 2018 at 6:24
  • I haven't yet. I must admit I'm really not the most knowledgeable when it comes to electrical issues. Where would I take that measurement? At the alternator?
    – Tobias
    Commented Feb 1, 2018 at 20:09
  • Take the measurement at the battery. You're looking for what the voltage is to at least one digit. So 12.2V or 14.7V just for example. Also look at how steady the voltage is.
    – vini_i
    Commented Feb 1, 2018 at 20:20
  • The voltage is between 14.2V and 15.4V, not steady at all, changing quite a bit.
    – Tobias
    Commented Feb 2, 2018 at 5:28
  • Some kind of weird coincidence aside I'd say that @HandyHowie is correct and the alternator rectifier bridge is failing. I'd suggest pulling the alternator and taking it to a parts store that can test it. Even better if you have a rebuild place in your area. They are kind of rare now a day.
    – vini_i
    Commented Feb 2, 2018 at 16:45

1 Answer 1

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My guess would be that one of the diodes that forms the rectifier in the alternator has broken. Your alternator is not providing a steady charge current which affecting the electronics of the car. It will also stop the battery charging which is what you are experiencing.

Checking the battery voltage while the engine is running will probably show a low voltage. Should be above 13 volts when running. An oscilloscope would show a pulsed output from the alternator if this is happening.

One thing you could try, is to fit a fully charged battery, and then remove the alternator belt, if that is possible. When the engine is then started, if the problem has gone and returns when the alternator belt is fitted again, then that would point the finger at the alternator. If the alternator belt also runs other things like the water pump, then make sure you don't run the engine for long, so that it does not overheat.

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  • The voltage is between 14.2V and 15.4V. I guess that means it's not the alternator?
    – Tobias
    Commented Feb 2, 2018 at 5:28
  • That voltage is a little on the high side, but that could be an inaccuracy of a cheap multi-meter. It still could be a problem with the alternator. I have also added to my answer.
    – HandyHowie
    Commented Feb 2, 2018 at 7:45

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