Internal lighting pulsing
 

I noticed last night that if I open the car door with the engine running, the internal/courtesy lights pulse.

I recently had the ancillary belt changed and wondered if it was related? Although it may have done beforehand but I didn’t notice.

I had this on a BMW and it was the diodes or rectifier on the alternator. Some removable (replaceable) electronic part anyway. Probably not replaceable seperately these days?