Had a few problems with the head up display which notifies bulb failures.In particular the rear fog lamp.

After changing the bulb which made no difference, i swithched the light switch to the fog light position and this did the trick. But it has left me puzzled.There are no details in the handbook and the owner is simply told to go to the main dealer.

Can anyone let me have details of the bulb layout just in case some previous owner has used the wrong bulb i.e the stop lamp has a double filament. and an explanation of the fault

Many thanks

Probably needed to see some current flowing to effect a a reset?

Q.

Handbooks are usually quite good about telling you which bulb goes where, if not a perusal of the bulb holders will show you whats what.

Most single bulb holders will be single centre base contact plus side earth with symetrical locking pin guides, applies to typical 5w side lights and 21w single stop or white indicator bulbs.

Stop/tail combined bulb holder will be two base contact side earth with offset pin guides. Easy to confuse those with amber indicator bulb holder which are single base contact with offset pin guides, but you'd soon know due to flashing.

Very unlikely to come across a twin contact single purpose bulb holder with no side earth contact on modern cars, but often found in some usually older commercial vehicle designs.

Thanks for all your useful guidance.

The stop lamp has been fitted with twin base contact bulbs but there is only one contact pick up in the holder.

Do you think these should be fitted with single contact bulbs?

Cheers