Hi dudes!
My mrs has a J reg 1.6 driver and it's doing something very weird!
Car idles fine until you turn on the headlights, then the revs go slightly up, down, up, down as do the headlights in brightness! Now my mate had the same problem on his Golf but didn't sort it before he sold it

Bad earth maybe? Dodgey alternator?
This common? Anyone know how to fix it?
Thanks!
