Temp guage reading wrong

[Schurkey]

I would have started a new thread with this same title, but I haven't done the same work. Temp gauge is pegged now all the time, is the first step to look at wiring or to test the sending unit? I see one on the driver's side in that head but don't know if that's the only one this orig 7.4L TBI has?

1989 C3500

"Pegged" probably means that the wire to the sending unit has a bare spot, and is grounding. Perhaps the connector fell off the sending unit terminal, and is touching the exhaust manifold.

Yes, I'd expect it to be on the driver's side cylinder head.