why does my Bosch oven light fail when I use the grill?

Probably just one of those things - Oven Bulbs are usually quite reliable - you were unlucky and got a bad one - it popped - as the vairous bits of broken fillament fell down inside the glass bulb they may well have caused a temporary overload and popped the fuse.

I suspect it was just a dodgy bulb - there is no way that use of the grill can damage a bulb.

Peccavi
June 2010