if you want to seal it up with any type of compound, you might as well not use a connector at all. A connector is used for easy service/manufacturing. Any kind of sealing compound, will make it impossible to disconnect it, making service almost impossible. run the wire directly into the passenger compartment and connect it there. alternatively there are several types of automotive connectors that are sealed or water resistant. even a standard utility trailer connector would work. but if you want to service it, don't glue it together.