[mark houghton]

I think one is ground, and the other is hot. Since that temp switch will open/close (like a relay) in response to engine temperature alone - whether or not the wires are connected to it - all it's doing is breaking a circuit. With that said, it shouldn't matter which side of the switch has the yellow wire or the red wire....I think. Unless the connectors themselves are different sizes, then it would be self-evident.

That's just uninformed logic talking. See what others have to say as well.