Fiesta mk7 wet seat belt problem

[Rogers4796]

Hello all after all this rain the wife has told me that the drivers side rear seat belt is soaked. Can't think of where the water has come from. It's a 3 door mk7 fiesta so no door seals for it to go though. Only thing I could think of is the gasket is no good on the light cluster. As anybody had the same problem at all?

[WES180]

Does the tube for the rear screen wash run along that edge? Drop the roof lining a bit by removing rear c pillar interior trims and rear roof grab handles (should be the same as my focus)so you can have a look. Check the the boot seal is sat correctly and not damaged too.