I have an Astra G 2.2. It was working just fine, no issues. Recently passed MOT with no advisories or issues.

Today I topped up the oil and replaced the overhead interior bulbs with LEDs. They aren't the "boy-racer" LEDs bought cheaply online. They are basic white LEDs designed and spec'd for the car bought from Halfords. They fitted no problem and worked great, still no issues.

I then took the car out for a drive and for the first 30 minutes things were fine. Then I was driving along and suddenly the red battery light came on and I lost traction control, ABS, powering steering and airbags (the warning lights for all these came on). The car was still running and I managed to drive home, very slowly and carefully.

The interior and exterior lights are still working, although the high beams won't go on. Radio, wipers and indicators will still come on, but the car won't start after I turned it off when I got back.

I also have the "Engine Electrical Fault" fault light on now.

I tested the battery with a voltmeter while still connected and the engine running and with the engine not and it clocks in at 9.10V.

I find it coincidental this only happened when I fitted the new LED bulbs in the interior but does anyone have a better idea of what this is?

1 Answer 1


tl dr - It sounds as though you have either a bad alternator, a bad battery, or both.

It could be the alternator which went bad and then allowed the vehicle to drain the battery. This seems most likely. You can check this if you have the engine running by putting the multimeter on the battery for a period of time and check the voltage. If it continues to drop, it's the alternator due to it not putting out juice to keep the vehicle running. When fully charged the battery should be ~13.1vdc ... With the engine running, a good alternator, and a charged battery, the system output should be around 14.1-14.5vdc. Each vehicle model is going to be a little different with where it runs nominally. ~9vdc is way low on all counts.

The battery could be bad. If you have a battery charger, put it on the battery and see if it will recharge. I would bet it will, unless it is an old battery which couldn't take the abuse of losing the alternator.

EDIT: I doubt it had anything to do with the LED's either ... they will actually put less of a load on the system, so ...

  • I couldn't see it being the LEDs either but the timing is just way too strange. When I test it and leave it running if it sticks around 9vdc would that indicate the battery rather than the alternator?
    – Flatlyn
    Commented Apr 25, 2015 at 2:49
  • @JamesKrawczyk ... try to recharge the battery to see if it's good. If it will take the charge, put it back in the vehicle and see if it will start it. If it drops without charging it around 14+vdc, it's the alternator. If it doesn't want to charge at all (or very little), take the battery to a parts house and have them load test it for you, at least I'm assuming they'll do the testing where you are at for you if you ask. Commented Apr 25, 2015 at 2:52

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