Troubleshooting Boiled Battery

Hi everyone, 304 V8 and I'm a rookie/village idiot mechanically.

Last fall I noticed the smell of rotten eggs after driving periods of 25 minutes or greater. Popped the hood and saw fluid boiling out of my battery terminals. Long story short, I thought it was my alternator and replaced it. During that replacement I found out external voltage regulators were a thing and mine had shaken loose and wasn't really grounded anymore (this is what I think was the root of the overcharging problem). I replaced that too, but now the car does not start unless jumped. It will remain running once disconnected, but requires a jump to restart immediately after shutting off.

Is there a way to test if my battery is now garbage without a min/max function on my multimeter? Another fun aspect is the tachometer installed by the prior owner no longer works while running, but the needle will bounce when I turn the key in the ignition. This would imply I goofed up on the reinstall, but everything on the new pieces got attached in the same manner the old alternator and regulator were affixed.

 

Thanks!

On the bright side, that puts it back in the "parts gone bad" column instead of the "I messed up the install" column

 

Sounds like you need a new battery, but most auto parts stores will do free battery testing if you want to be sure.

I would double check your tach wiring before installing a new battery. Sounds like something may be wired in backwards. I believe green wire normally goes to the negative side of the coil, black to ground and red to ignition.