Headlight leaks

[C M Smith <cmsmith@domain.elided>]

As the owner of a small trailerable sailboat I'm aware of the phenomenon of 
hot wheel bearings getting wet when cool ones are water proof. Immersing 
the hot bearing in cold lake water causes drop in pressure inside the 
bearing sucking water in where normally the grease would keep the water 
out. Always let the trailer cool off before launching the boat!

The problem with the headlight might be the cooling effect of wash water or 
rain water on the otherwise sealed unit. Cooling the headlight might cause 
the air pressure inside the light to drop, sucking water in through a 
defect in the seal not detectable under normal temperature and pressure 
conditions described in your testing. A relatively small temperature drop 
can produce a pretty powerful vacuum effect, sucking water in where 
normally it would not go. The most likely place is the top joint between 
the lens and the reflector where water might sit long enough to find a tiny 
flaw in the seal and get sucked in, so to speak.

Just a thought.


Michael Smith
Calgary, Alberta
Canada
91 Alfa 164L, White, original owner

------------------------------