Downside to sealing rear roof running lights?

[brad1]

I was just up on the roof installing a fan cover and noticed that one of my rear roof running lights has a pretty big gap between the metal of the fixture and the aluminum roof. I can see that there is a washer in there of some kind, but it's pretty exposed. I'm guessing a lot of water gets in there when it rains, and even more if it rains when we're running down the highway. (Cue Doobie Brothers song).


Is there a downside to sealing the gap with silicon sealant?



I haven't had to replace a lamp in any of those fixtures and don't know if something like a sealant would make the project more difficult, or even require the breaking of stuff (which many of my repairs seem to involve).
As a bonus, I'd like to hear how you do replace the bulbs should that become necessary.


Thx and travel down Hwy 1 from San Francisco to Santa Cruz, Monterey or points south next spring. It's f'ing gorgeous right now.

[AKNate]

We just had ours at the dealer for this exact problem. Water was leaking around the lights and running down inside the wall and came out a sheet metal seam by our rear bunk when it rained heavily. They resealed the lights. I’m not sure if silicone is what they used or something else.

[BayouBiker]

The sealant makes it a bit but not much harder to replace the lamp. If you take the lens off and seal both sides of the gasket, silicone will work okay. if you just seal the gap as is, without removing the lens, you should use a high quality flexible polyurethane sealant. Airstream likes AdSeal Sealant Adhesive. I like Silkaflex 221. Silicone does not have good sheer strength and tends to crack after a year on trailers so it should be avoided.

[pjshier]

...and Silicone tends to make aluminum unhappy. Non-silicone alternatives abound - earlier in this thread and by search ("sealant") of other threads.

Now going to find my ladder to check my lights...

[SuperTrouper]

I asked an old Harley tech one time how to permanently seal my turn signals to make them water tight. His answer was "don't". Water will always find a way in, make sure that it has a way out. Since then I drill tiny weep holes or leave a tiny gap at the low point of the lens seal on exterior automotive lighting. I also resisted changing my exterior marker lamps to LED because the incandescent lamps get warm and (hopefully) help dry out the fixture when it's not raining. If you insist on a perfect seal, you might wanna buy some blinkha fluid and fill the fixtures before sealing! ;-)

https://www.youtube.com/watch?v=E6GsXhBb10k

[dhroberts]

Originally Posted by brad1

I was just up on the roof installing a fan cover and noticed that one of my rear roof running lights has a pretty big gap between the metal of the fixture and the aluminum roof. I can see that there is a washer in there of some kind, but it's pretty exposed. I'm guessing a lot of water gets in there when it rains, and even more if it rains when we're running down the highway. (Cue Doobie Brothers song).


Is there a downside to sealing the gap with silicon sealant?



I haven't had to replace a lamp in any of those fixtures and don't know if something like a sealant would make the project more difficult, or even require the breaking of stuff (which many of my repairs seem to involve).
As a bonus, I'd like to hear how you do replace the bulbs should that become necessary.


Thx and travel down Hwy 1 from San Francisco to Santa Cruz, Monterey or points south next spring. It's f'ing gorgeous right now.

I am the process of dealing with some filiform corrosion near one of my roof running lights. My repair required that I remove the existing light to determine if the corrosion went under the light (it did not!). The light has a solid, flat 'rubber' gasket that runs the entire surface of the base of the light fixture. It looks like a white colored product such as Silkaflex was used between the roof and the gasket.

My guess is that silicon is not advisable given that it gets brittle over time and is not UV resistant. Best to pursue a durable fix.

I assume that you will be taking the light unit off the roof to determine the extent of your problem. I purchased a new light unit from High Sky RV Parts - will use the new light module and the new 'rubber gasket with the original metal base (not the plastic base unit that was sent). I plan to apply a thin spread of Silkaflex across the entire gasket surface prior to screwing down the light's base plate onto the roof. If I am not 100% satisfied with how the base plate lays on the roof, I will seal the edge with Acryl-R sealant.

Good luck.

FYI, on my 2016 Classic, there is no bulb to replace as the running lights are all integrated LED units. That's why I bought a replacement light unit and only use the parts that I will need.

[KevinFH]

I recently took off the rear center roof light (2016 FC 28) to steal power for a backup camera. The LED marker light had a gasket built into it, however there was no additional sealant used. The gasket is starting to get old now. When I reinstalled the light, I put self-leveling Sikiflex on the screw holes and all over the wire entry grommet before scewing the marker light base down to the trailer. I don't like to goober everything up when the entry point is a small screw hole. Of course, I have Sikiflex all over every finger and on my clothes, but on the trailer it is only where there is a hole in the aluminum. I did not want to havwe to remove the lights with a crow bar next time.