mk7 transit mwb rear passenger light short and fire

[BRADMURPHY]

hi wondering if anybody could help me my transit rear light cluster and housing have caught fire and melted while not in the van luckly spotted very quickly i have since checked the loom that goes in the back door panel and all is fine i have purchased a new ligh board and lense unit before i fit i will be cleaning and re painting and re earthing the connections is there anybody with any wiring diagrams or have witnessed this before as i have seen they say water can get into the light cluster and allso the connections corrode and short i just want to make sure everything is correct before fitting the board and new cluster for it to happen again many thanks