Greg wrote:

One other trick is to coat the connector with RTV, then slide
the heat shrink over it and apply the heat. The shrinking heatshrink pushes
out the excess RTV and makes a very water tight seal after it cures.
Good luck with it,

Any seal that relies on RTV will take more than luck. RTV will fail to
seal and water will wick into the connection and destroy it. It is as
predictable as sunrise.

There are many off the shelf connectors and sealing materials for that
application and nearly all of them are far superior to any of the
silicone adhesive sealants so often misused by the DIY'er.

Rick