[Peartreeproductions]

About a week or so ago I noticed that shortly after I pull up behind a car at the traffic lights I can see my headlights dim slightly. It only happens for a second or so. Since then I have also noticed it whilst driving along without the clutch dipped.

The fan belt doesnt sqreech or squeel and as I said it is now happening whilst on the move so it cant be the effect of the power steering. Any body got any ideas or had the same problem? I have searched the forum without any success but from experience with other cars it seems like an alternator fault

By the way I have an '03 MC.

[supercharged]

I could be worn bearings on the alternator or one of the parts that run on the fan belt. My friend's 3 series just had a problem like than and eventually the belt snapped.

It could be many things, but that's one thing that I know of that could give you some idea of what could be causing your problem.

Good luck

SuperCharged

[cooperblack]

I have got the same problem i notice it when i start up in the mornings it's done it from new it is now three years old and still does it no problems so far !
would be interesting if somebody could shed some light on the subject (no pun intended)
bit late for me if it is a problem that could of been fixed by warranty.

[Malin Dixon]

I don't think you have a fault at all. The battery is probably just a bit more tired than when it was new.

Alternators are slow to respond. When electrical things turn on, the entire extra load is taken from the battery for about 1/2 second until the alternator can wind up its output current to match the new load.

As you slow down, the power steering pump or the fan may come on. This load, and a battery that isn't brand new, means that you can see a slight dimming of the headlights.

I would certainly not go and change the alternator unless you find a more definate problem.

[cooperblack]

I think you have the wrong end of the stick, it is a missleading description,
the fault is a sudden dimming like putting only say 9volts to the lights it is only for a split second or two and then it goes back to being normal brightness,
I find it hard to check it out as it is not a constant drain i have used an AMP clamp on the alternator output and it is running at full power at all times except when i put a load on the system.

[morrisminiminor]

If you find that your battery is not charging properly, other strange things may start to happen. My car has a low mileage 10K after 3 years. See faults & fixes but I'm told that buzzing/juddering around the speedometer area is due to a 1/2 charged battery. I've been told it would take an extended run up to 200 miles to fully recharge the battery. Looks like I've got a dynamo fitted to my MINI.

morrisminiminor

[Peartreeproductions]

Quote: Originally Posted by Malin Dixon

I don't think you have a fault at all. The battery is probably just a bit more tired than when it was new.

Alternators are slow to respond. When electrical things turn on, the entire extra load is taken from the battery for about 1/2 second until the alternator can wind up its output current to match the new load.

As you slow down, the power steering pump or the fan may come on. This load, and a battery that isn't brand new, means that you can see a slight dimming of the headlights.

I would certainly not go and change the alternator unless you find a more definate problem.

Yeah Malin I think you have the wrong end of the stick - I didnt explain that the dimming is very sudden and only lasts for a short time. I dont think that when travelling at 60 mph in more or less a straight line that it could be only due to the slow reaction of the alternator. I will take it in to see the dealer soon for its first MOT so will see if it needs looking at under warranty.

Thanks for all your replies, will let you know what the stealer says!

[MiniService]

malins post makes perfect sense, you said in your orignal post shortly after coming to a stop, not when your driving at 60 mph, which is it?

[Peartreeproductions]

Both!