BF2S Forums Car shit again

TheEternalPessimist wrote:

OK so my battery is losing charge, battery charge warning light thingy is on but only dim.  Removed battery, fully charged it, tested it, gives ~12.5v with the engine off so that seems fine.

Tested with the engine running it drops to 11.6v so I'm guessing my alternator is farked as the voltage should be closer to 15v with the engine going, basically all I want to ask is there anything other than the alternator which would cause this sort of thing? I like to be pre-informed before I let a mechanic try to bullshit me out of my money

Afaik the alternator is the only thing that charges the battery when the car is moving.

Other things that can affect the battery are a short somewhere in the wiring loom (unlikely, but expensive), inadvertently leaving something (lights, radio) on.

Christbane wrote:

start it and disconnect the battery if it kills there is for sure a problem with the alt.

I've seen that result in stuff dying so I'll give that a miss (it's a diesel btw if that affects anything ), i did think about a short, the only other thing is a blown fuse possibly? i dunno, I just make educated guesses, I don't know much about cars.

Gonna have to hit the sack now, thanks for the suggestions, I'll pop back in here in the morning before I start phoning garages.

I want to ask is there anything other than the alternator which would cause this sort of thing?

Voltage regulator, which is usually part of the alternator these days.

start it and disconnect the battery if it kills there is for sure a problem with the alt.

Noooooo....

Take it to an auto elec, they can test it in about a minute.

Could just be the alternator brushes need to be cleaned/replaced. If so chances are the commutator is near death so easiest to replace the whole alternator.
You could also have a partial short or moisture somewhere, good luck with that.... can be due to a really dirty/oiled engine.

Protip 1. Don't drop a spanner across your battery terminals with the engine running.

Protip 2. If you jetwash your engine bay remember to wrap the electronics in plastic, or you'll be stranded at the jetwash place for a few hours....

Last edited by Dilbert_X (2010-04-26 17:00:12)

Dilbert_X wrote:

Protip 1. Don't drop a spanner across your battery terminals with the engine running.

Been there, done that!

/ZINGA!

Just take out the 3 bolts that hold the thing on and go have it tested for free at your local parts store?

Recon exchange units are reasonable.

Use a multimeter and test the output of the alternator on the big fat cable coming out of it, it should be 13.6-14 or so. 15V is a bit too high and you would be frying your electronics.

If it is putting out 13.6V or better i would replace the big fat cable (B+ cable)

edit- Also check the cable going from the negative terminal on the battery to the chassis, you may need a fatter cable

Last edited by Nappy (2010-04-27 02:13:42)

Varegg wrote:

In many alternators you can replace a couple of carbon-brushes and the alternator is good as new again ...

Could well do, mine lasted a year after changing the brushes, the new ones wore out in that time due to the commutator being worn.
Its not that simple on many units though. For the hassle of changing the alternator on a French car I'd just stick another unit on.

Getting a replacement shipped form a salvage yard for £40inc VAT and shipping costs, 3 month warranty on it, so that's not so bad, I may possibly be considering another car by then (depending on the financial situation) so if it fails I couldn't care less Hopefully my cousin will fit it as he only charges me in crates of lager, which I can get cheap Failing that my local garage has quoted £40 to fit it, so all in all it's not horribly expensive.