Battery light

[Cats]

What's the thoughts on the battery light coming on intermittently when driving i.e. not idling stationary. In the dark noticed the headlights dimmed slightly at the same time.
Car has just been serviced.
2002 450.

[Trevor450]

Check 100A fuse, slipping belt,alternator and battery in that order. Most likely its the fuse breaking down.

[Steve_D]

Don't just 'look' at the 100 amp fuse take it out. The standard fuse is just thin metal and the fuse holder is bolted to the underside of the engine mount.
The most common failure mode is a fracture caused by vibration and is very difficult to see hence the suggestion to take it out. Being a fracture could be causing your intermittent volt drop particularly when drawing headlight current.

Steve

[N7GTX]

This is what you are looking for. The fuse is a flat metal strip so is called a strip fuse.



Once you find it, replace the fuse with one like this. They do not crack and are very reliable. TVR Power fit these as standard. The fuse is a straight swap. It is called a midi fuse.

[Sardonicus]

Agree with previously mentioned above but if the above all checks out including security of terminations from alt unit to starter then you could be looking at signs of worn alternator brushes or commutator or both that an auto electrics shop can turn around cheaply rather than changing the whole unit most will give you a before an after alt health bench test print-out too