When I moved into my last house, I had a fun electrical problem. We moved in October and I would end the day by taking the trash out. Now, my garbage can was outside the door from my garage to the backyard. One night the light outside that door didn't go on. It was late, so I figured I'd look at it the next day. Worked fine all day, then at night it didn't work again. It was a new house, so I called the builder.
The electrician came out to check it and gave me the most incredulous look when I told him it didn't work at night. But he went to take a look. Came back later and said that the wire was barely touching the light fixture. So, at night, when it go colder it would slightly pull back and no longer be touching. During the day it would warm up, expand and would work just fine.
my wellhead does this when it's below 20F outside. Oxidization on the wires throughout the year mean that any shift of the wire causes a disconnect.
haven't figured out a solution, i just run a drip that is loud enough i notice if it stops so i can go out and reseat the wire, otherwise the stuff outside the well can freeze and that costs money to replace.
Sounds like you just need a better mechanical connection. There are silicone-filled waterproof wire nuts available. Maybe if you clean the wires and secure them with those all will be good?
The electrician came out to check it and gave me the most incredulous look when I told him it didn't work at night. But he went to take a look. Came back later and said that the wire was barely touching the light fixture. So, at night, when it go colder it would slightly pull back and no longer be touching. During the day it would warm up, expand and would work just fine.