[MrSchaeferPants]

Your temp gauge should peg out if grounded. Like said above, two green wires, the horn on mine is a normal female spade.

If you can't connect the temp wire to a ground (because the shape of connector) grab a jumper wire and hook it to ground, if it doesn't max out the gauge, you have something else wrong. Don't quite remember troubleshooting senders, as I almost never have one go bad. But the colder it is, the more resistance (ohms) the hotter it is, the less resistance. I suppose either a manual, or manufacturer of that sender would have the ohms numbers to check.

But I'd start with grounding the green wire, then trace (visually) make sure it goes to the dash, and to the temp gauge, then if needed start tearing that apart, make sure the wires are there, secure, in good shape, etc.