Just wondering if anyone can help. On the tailgate of a E46 touring there is a set of light clusters which has the fog light and reversing lights. On my car they have turned dark and look out of place next to the clean main light cluster. They seem to be dirty from the inside and would the old concours trick of dashwasher-on-header-tank tip work on this. This sounds silly but can they be cleaned and if so what would be the best way of going about it.

Sorry for a slightly pointless thread, but it is something which i annoying me.