A strange one here when I put the side windows up my headlights dim then go back to normal once I let go off the up switch.

Is this normal?

Na not really normal. What happens when u use more power? Ie open windows and put the heated screen plus ac on at the same time.

It could be your alternator isn't charging the battery enough. So if the battery isn't getting 14volts when it needs it, it will struggle to power things.

Check charging rate an what output is in amps for ur alternator an what size is ur battery is but it does happen if just sitting idling ur puttin an extra load on it if battery good an it's charging I wouldn be worried some people buy higher output alternators an bigger battery this can help

if your sitting there on idle i would say this is normal the power has to come from somewhere

My wife's Clio does the same. You can hear the relay switch in which is taking power directly from the battery which makes the lights dim slightly and then you can hear the relay switch off when the window has reached and the lights brighten again. There is no issue with the battery or alternator.

Normal, my Almera does the same

Thanks guys for your feedback good to know everything is sound. Guess it's a bit strange to see haha