Lights dim when brake

[Guest]

Morning all,
I have had my ForFour for just over 3 weeks now, and last night was the first time I have driven it at night. I noticed that when I brake and change down gears, the rev's dropped like they do, but also the lights dim. This is only briefly while the rev's have dropped. Any ideas of the cause? I have got it booked in to MB of Ipswich on Tuesday for other little jobs but just wanted to know if it's anything that I can look at before it goes in.

[J500ANT]

Re: Lights dim when brake

Im not sure why but my hunch is that the battery is knackered. If it requires the engine power (ie alternator) to get the lights nice and bright then I reckon the battery could be a bit iffy.

But what do I know?

Tony