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My partner's Micra SE (2006) has had starting/electrical issues for a while now. Multiple mechanics have diagnosed bad batteries and replaced with the problem returning within days/weeks of the replacement.

The starting issue manifests as either a repeated rapid clicking or a very slow, laboured revolving noise and no start either way. Can be started by jump starting the car.

The other electrical issues have come/gone however the one that remains is no reverse lights. Bulbs have been replaced, they don't work even brand new.

My belief is that it's an electrical issue overall (most likely a drain leaving the battery too low to start the car although the car can be put into accessory mode for considerable time even at this point with no issues). I've tested the voltage across the battery at various points and it's as such:

  • Car Off for some time: ~10.2-11.5v
  • Car just turned off: ~12.9v*
  • Car on at idle: ~14.4v
  • Car revving to 2-2.5k rpm: ~14.4-14.5v

The car can be restarted fine if just turned off, however leaving for even a few minutes it won't start. If I keep the multimeter connected after turning the car off, I can see the voltage drop by 0.01v every few seconds though I haven't seen at what point this stops (if at all). Also, with the car off, the rear right reverse light appears to be pulling anything from 1-6v constantly (checked by inserting the multimeter probes into the plug that connects the rear lights).

I've checked 2 of 3 fuse boxes (the third under the front left headlight is a pain to access so I haven't done that yet) and all fuses seem fine.

I'm far from a mechanic and only have a rudimentary understanding of electrics. Just want to confirm if my thinking is correct and where the next places to look would be?

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  • "Also, with the car off, the rear right reverse light appears to be pulling anything from 1-6v constantly (checked by inserting the multimeter probes into the plug that connects the rear lights)." You are surely on the right track.
    – Beni Bogosel
    Feb 16 at 12:24

1 Answer 1

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You need to connect your multimeter as an ammeter in series with the battery and check how much current is being drawn from the battery when everything is turned off. The current should likely drop below 100mA is everything is working as it should.

If there is a significant current draw, unplug each fuse one at a time to identify which circuit is causing the issue.

It could be something as simple as a faulty tailgate lock switch that allows the boot/trunk interior light to stay on when the tailgate is closed, as my next door neighbour has experienced.

It could also be a fault in a circuit that is keeping one of the computers powered up when it should have shut down.

Identify the circuit drawing the current, then report back with your findings.

Just to correct a mistake in your question. Your wording about the reverse lights pulling 1v-6v is incorrect. Electrical loads don’t pull voltage, they pull/draw current. There may be 1v to 6v appearing on that connector with the bulb disconnected, but that doesn’t necessarily mean there is any significant current behind it. This could however still be important as far as your issue is concerned, so you could start pulling the lighting circuits that handle the reverse lights. Have you tried leaving the reverse lights disconnected to see if the battery drain stops?

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  • Fair point on the correction, poor phrasing on my part. I've had the ammeter connected in series previously but by the time the battery is down at 10.2v or so when I've tested, the current is absolutely 0. However, I'll give it another try after it's just been driven as I suspect the findings will be different.
    – Daniel D
    Sep 18, 2022 at 10:27
  • A clue may be with reverse light wiring possibly shorting out the battery or incorrect replacement tail/brake light bulbs. Perhaps removing those replacement bulbs overnight, measuring battery voltage after bulb removal then again the next day may reveal whether or circuitry or incorrect bulbs is creating a severe battery drain.
    – F Dryer
    Sep 19, 2022 at 1:02

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