As a counter to the good Mercedes comments, our C class saloon had rear brake light wiring burn out. When I investigated I found that the earth return for all the lights in the cluster was exactly the same thin wire as the individual feeds so rear fog plus sides plus brake lights were all returning down one thin wire. It overheated where there was a junction and burnt through. On the net I discovered that this was a common problem and in the US had justified a recall of all cars involved plus several legal claims for burnt out cars In the UK, with a totally ineffective consumer protection setup, there was no recall.
Merc refused to help. How they could justify this attitude I really dont know - burnt out wiring inside and unmolested shouldnt happen even on a 50 year old car.
