I am okay at DIY projects....sometimes it comes down to not enough time in the day to do everything, so I hire professionals to do the work. (So I think )...I can't tell you how disappointed I am with some of the trailer shops I have worked with. I have paid twice to have my trailer rewired in the last 2 yrs...both times I asked for them to not use waterproof connectors like these.
I ended up tearing into my harness this weekend after lights went out again, and found not one but two of these connectors in line for my side marker lights. When I was in the CG I learned a tip from an old salty MK engineer...he used silicone with his connectors...we never had issues with corrosion. The below photo is an example...I used heat shrink connectors along with the silicone. The key is to pack it in tight so no air/water can get in. I did this on my last trailer and it went 5 + years with no failures. I guess the old theory if you want it done right, DIY. Hopefully I will not be dealing with this again for awhile...if so I just might go to blows with myself.
these connectors suck!!!