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Car Paint & Silicone - Do they love each other? My trucks over cab running lights are leaking

Can anyone suggest the best way to seal the overhead running lights on my Ford Truck F550 2001. The inside of the cab is foggy everytime it rains, I’ve cleaned all the gaskets around the doors, pulled and cleaned under the shield between hood and windshield where wipers mount. I can see moisture inside the running lights. My solution… a bead of silicone under each running light. Friends and auto shops say silicone will corrode the paint. True or False? The moisture inside the cab is ruining my electrical components. Already paid to replace headlight switch, now windshield wiper motor is crying. Don’t know steps for reverse rain dance. Is Silicone on Painted surface ok or trouble ?

I would not think it would cause any damage. It’s used all over the house and paint does not peal. I would definitely use an exterior rated CLEAR silicone for windows/doors. Put a small bead where the lights seal and a light coat on the cab side where the wires penetrate the cab.

I agree. I used some to seal a leak in my trunk due to bad trim screw seals. That was over a year ago, and no more leak or damage to paint. The trick is to pull the lights out and seal the holes underneath it. Running a bead along the edge of the light will look bad and eventually peel off.

Thanks! Common sense prevails. That is exactly what I wanted to do but was scared away. I’ll pull the lights, clean and use my favorite clear silicone.

p.s. Also I do like the suggestion of sealing the thru body hole rather than around the light base. I’ll let you know how it works out when I’ve finished.


I’m going to be a spoiler here . . .

I think it’s possible your front windshield needs to be resealed . . . that is, removed, and reinstalled, using fresh sealer

I’ve seen this problem before, and the symptoms were identical to yours. Foggy interior when it rains

Remembering that water condenses out of the air on cold surfaces, I am wondering if we are just talking about water in the passenger compartment - having been brought in on the soles of people’s feet - condensing on a cold windshield. -

Not to mention the vents into the passengers compartment when the outside air is humid but warm.

spoiler, yes first place I started was at windshield shop. It was replaced 5 mostly dry years ago. Windshield Tech suggested cleaning gaskets and under shroud. Last summer was record rains and that is when the inside cab fog was as beading as bad as the outside rain. Truck mostly sits right now as life demands attention in other places. Hopefully wet feet and dirty carpets this year. I’ll check the vents, might even tape them off just to see. All good suggestions.

I think instead I would go to an auto parts store and use an auto body sealer instead. It is more likely to stand up to the rigors of the outdoors and sheet metal expansion/contraction.

Well the fog in the lights seems a reasonable suspect, do you have a sunroof? That is the second most likely suspect.

No, sunroof only wishful thinking for a farm truck. I just checked the vents on back wall of cab. Flappers on vents are in place and still pliable. I’ll have to pull dwgs to find other vents. I see an equipment shed in my future…