When we came out of the carwash, one of the lights was missing from the top of the windshield. We found the lamp again and now find it is loose. What do we need to do to make sure that it will not leak when going through the carwash next time. Suggestions please!

 

Tighten them. you could use lock tight I suppose...

 

if you mean one of the three marker lights in the middle, then it might be broke and you might need to RTV it.... if you mean the amber clearance lights on the sides, then it is supposed to have a screw in it.

 

Use a silicone sealer to make sure the lights are watertight. Some folks get water leaks from those areas. Personally, my cars would never ever see a car wash. It just wrecks the paint. All the debris from all the previous cars who have used the car wash is still in the brushes. Just like sandpaper. I can spot the swirl marks a mile away. And the touchless car washes use such high pressure, that some paints can't even withstand the force and start flaking. But it's everybody's own choice