Temperature gauge pegged??

[Thor94]

Ok, I need help...

72 C20. Truck had a motor swap some time ago, never had the temp gauge hooked up. Bought a new sending unit, and was planning to install it, but noticed my gauge is pegged right/hot all the time. Regardless whether the key is turned on or not.

Read through the forum threads, saw the diagrams, common issues , can't seem to figure out why it's pegged all the time.

Found this handy diagram on here...

-Seeing 12V on the post at 3 o'clock.
-Seeing same 12v on the post at 9 o'clock. Going off to sending unit.
-Found dark green cable leaving bulkhead, followed it.. it's disconnected in engine-bay. Seeing the same 12V on the disconnected end.
-Ran continuity test from green-cable (engine-bay) to gauge post at 9 oclock... looks good.

I would expect since the sending unit is disconnected in engine bay, the gauge would read 'low/left'? Not pegged high?

I tried to jump ground on post at 6 o'clock to ground...nothing, still pegged.

Now, granted my sending unit is still disconnected, but shouldn't I see that needle move a little left at some point?

Oh, also pulled back circuit board from posts at 3 and 9 oclock.. no change.

Bad gauge? Is my logic flawed? Do I just install sending unit, and keep my fingers crossed???

Help!!!

[special-K]

Sounds like a dead short

[Korted]

If the green wire is shorted to ground, it will read full-hot. If you remove the green wire from the gauge, the needle should drop to cold. If it doesn't, you have a gauge problem. From your note about 12V on green wire in the engine bay, I suspect gauge problem.

[Thor94]

Thanks for the replies.

By pulling back the printed circuit board, I'm essentially disconnecting the green wire from the gauge. When I do that, it's still pegged. I'll probably just replace the gauge. Time to start researching that process.