Odd experience this afternoon in my 94 GMC 4.3L standard cab

[thx1138v2]

FYI
Coming home from the grocery store I noticed the tach and the speedometer jumping wildly all over the dial. I pulled up in the driveway, let it idle for a bit, and then gunned the engine. Sitting still in the driveway the tach and the speedometer were still both jumping all over as I gunned it. I turned the engine off and there was no electricity to any of the systems in the truck. I measured the battery voltage and it was 12.81V. Further explorations revealed a loose ground cable to the battery terminal although it still looked and felt connected. After removing it I found corrosion on the cable end and the battery side post. Cleaned it all up and replace the terminal bolt and every thing is OK again.

I'm guessing the loose cable was bouncing around on the terminal and causing the tach and speedometer needles to jump wildly. Don't know for sure.

 

[Nad_Yvalhosert]

Sounds reasonable...

Have a problem
Found a loose part
Tightened loose part
Can not duplicate problem

 

[HotWheelsBurban]

I know my Burb, if either of the side terminals get very loose at the battery, it gets squirrelly. Doesn't want to start right up, voltmeter is not where it normally is, stuff like that. And by "loose" I mean an eighth of a turn. Cable still feels tight and doesn't move when grabbed.
That's why I keep those wrenches in the passenger side door pocket. Once I get my underhood box in, I'll put them there. And my cables are very clean as are the mounting surfaces on the battery. The long positive cable is only a couple years old; when I replaced it, I checked the others and tightened/cleaned grounds and mounting surfaces. These trucks have so many computers, and they're really sensitive to voltage fluctuations.