one of my fog lights is dull and it failed mot.

one bulb ( drivers rear ) is duller than the other.

changed the wire that runs to the main fog but still no joy. changed the bulb also and cleaned the reflective part of the lense

any ideas please.

is the inside of the lens dirty, and check the wattage of the bulb itself! make sure it's the same as the other side, cos that size buld comes in two differant wattages

cleaned lens and swapped bulbs over till the same.

its only supposed to have one. Remove the pass side one and the drivers side will burn twice as bright

If you want to keep both (although I'm in agreement with Early-1800 that you only need one!) then you could try a separate earth lead (brown wire) from the lamp holder to a shiney bit of bodywork.  There should be an earth source already for the offside lamp holder ….. but it may not be perfik

see:

The Road Vehicles Lighting Regulations 1989

Cheers

If the other lights are fine but its only the foglights dim, its not the earth. It will be the wiring or the fusebox or the switch, worth a look and wiggling things etc.

i'll have another go later will double check the wattage of the bulbs