Re: Strange temp guage operation on YJ
Yup, sure sounds like a bad ground. Probably getting it's ground through the shifter cable now.
Think about it - the battery is grounded to the engine - else it wouldn't start.
But the body is isolated - engine & tranny are mounted in rubber mounts. It has to have a good ground strap between body and engine. Doesn't hurt to also have one to the frame too.
Easy way to tell - hook jumper cables between the body to the engine. See if it works properly then.
And/or -- strange but I've seen it more than once - the wire close to the temp sender - rubbing something - the insulation gets worn through. It tickles against ground when the engine torques over just a tad.
He He - had a customer once - Chevy, couldn't back up, it'd stall every time. You could put it in reverse (auto), no problem, take your foot off the brake and it would stall. 2 rebuilt transmissions, lots of bills from shops all over town. Deemed "unfixable."
He He - what it was the wire to the starter solenoid from the coil's resistor bypass had rubbed bare. Under just the right circumstances, it grounded out and killed the engine.
A real hair puller (that's why I'm nearly bald.)