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Battery Charging problems

Posted: Fri Nov 08, 2019 4:28 pm
by Renesis
Bit of background info, my car is a 2005 1.9tdi Passat and has approx 180,000miles on the clock with, I assume, the original Valeo alternator.

I was driving to work today via a different route and didn't notice a speed bump in the road which had not been painted yet (the small square bumps, not the large ones that span the road). Unfortunately I was carrying a bit of speed because of this, and hit the speedbump with some force. I heard a clunk - as if the bump had hit the underneath of the car.

I pulled over to have a look underneath and all seemed well so I carried on. About 2-3 minutes later, the battery light came on - checking voltage at the battery posts, I'm getting 12.5v at idle. When I accelerate hard to 2-3krpm the light goes out and the alternator starts working (based on interior lights getting brighter), but the millisecond I let of the pedal, the light comes back on again.

I bought a brand new battery 6 weeks ago, and in the time I have owned the car (5ish years) I've never had any issues with charging. It makes me think the bump has caused/knocked something but could this be a failing alternator / voltage regulator? All connections behind the alternator look sound, but I have no idea where the earth strap is in the engine bay (or if there's multiple) so just wanting to make sure there's nothing I need to rule out before shelling out for a new alternator/regulator.

Cheers all