lights!!!

[al 350i]

my lights were working fine up until the other day when the drivers side main light bulb blew, was taking car on trip next day so robbed one out of van! turned lights on and all seemed fine but never checked high beams. only noticed yesterday that i can turn lights on, pods come up and side and dipped beam work fine but when i put high beams on the 2 square driving lights come on but the main lights dim to side light!!!!

i've checked old bulb which is an E7 and new bulb is H4, the old one seems to have a higher power output but can't how this could make a difference, they are both 3 pin bulbs, i've unplugged it and it makes no difference.

any suggestions??

[superwedge]

sounds like a bad earth,