It is interesting how many Fusions have bad water ingress in the rear lights. Mine is a 2009 with water in both, despite sealing the bulbholder and everything else. Looking at Ebay and scrap yards I've found most of them to be the same when you ask or examine on a wet day. Even a 2011 car with water in both lights.

Is it a manufacturing problem as a local dealer said he had replaced stacks of them. Nice, as they are £100 each inc fitting or £75 if you do it yourself, and only a 12 months warranty.

I have had cars all my life and never any water ingress, only plastic fading on son's 2001 car.

The Fusion lights must be badly designed or very cheaply made!

I've drained mine a few times now and dried them with paper towels and a long screwdriver only to find they fill up after a bit of rain. Also had a go with silicone sealant to no effect. So have now drilled a small drainage hole at the lowest internal point of the light unit and problem solved. If I cannot stop the water getting in then let it have a way out

Yes that is good advice. After sealing one (the bulb holder and edges) there was no water in the bottom two thirds but large rain splashes in the top part. Can't for the life of me see how rain is getting in at a higher level! There is so much water in the other that it has to be getting in via the gasket which is always soaking wet, yet fixed correctly. Have bought one from the scrapyard for £20 with no water ingress as it has rained for the last 40 days and saw it on the actual car. So will see if water gets in, if it does I'll drill that hole!