It's a violation of NEC to make a splice in even low voltage applications outside of a junction box? Really? Then I've never seen a correctly wired furnace's call for heat/call for cold lines.
Chris, you know the splice is there, it's eating you up inside, I tend to think that no matter how much we assuage your fears that you'll still listen critically to your surrounds, thinking.. maybe... did I just hear that...
Do whatever it is you need to do to make yourself feel good about it. As is, his fix will be good enough unless you've got a really long run... if marretting a new piece of 12ga in there is what it'll take for you to feel okay about it, then do that, if crimp-on butt connectors is your "minimum" - do that, solder and shrink tube or just replacing the runs... whatever is going to keep you from wondering whether or not you hear something "off" back there.
Bren R.
