3406B coolant temp sensor location

Got the ‘87 379 Pete home, that I just bought yesterday and I’m needing to figure out why my heat gauge isn’t working? Where’s the coolant temp sensor located? 4MG 3406B engine.

 

I’ve found it. You’re suggesting that I ground that wire, while key is on and if gauge is good, it should go to, “hot”?

 

I probably should start a new thread but since y’all know you’re stuff, I’ll test you. Took the battery box cover off and there were 4 wires chewed through going to a solenoid on the inside of the box. The solenoid has a hot wire from a battery, a brown and black wire going to a 30 amp two post fuse and then the two wires go into the firewall. The brown and black wire are on the same small post on the solenoid and hot wire from the solenoid to one post on the 30 amp fuse. A brown and black wire come from the 30 amp fuse also. Basically there’s 4 browns and 4 blacks, that all got chewed through and I’m not sure which go to which or what their for?

 

That line is rather thick, for just an electrical line, was my first thought.

 

Here’s that little 30 amp fuse/relay. The hot wire on it went to the solenoid. The opposite side post on the solenoid went to + battery. The solenoid has two small terminals on top. One has a white wire to - ground, the other is not used.
The other post on this relay/fuse had both brown and black wires stacked.