Battery or Alternator or both?


Dec 19, 2016
Don’t drive my ‘78 much as I was doing brakes, etc. Charged battery, put in back in and drove around. Stalled a few times around the block and battery dead by the time back. Recharged and checked with battery and alt tester. Came up alt was overcharging. Put in another battery and came up overcharging. Figured it was the voltage regulator but actually can’t find it in the car. Not on the back of the alt or anywhere. Any thoughts?


Master Mechanic
Dec 16, 2011
Central NJ
That's correct it's internal.

The battery might be smoked as well.

Best practice, if you have a real charger, put it on a low amp charge for 2 hours, then a medium amp charge for 2 hours.

See what the voltage reads at the battery after the 4 hours. If 12+ volts, do a load test and see if it takes the load and comes back up close to 12v. If not, replace it.


Thread starter
Dec 19, 2016
Thanks guys. Was hoping it was one or the other but probably best to assume both are bad.
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Captain Tenneal
Supporting Member
Dec 26, 2013
Here's the deal: if the alternator is bad, it'll take out the battery and the reverse. It's easier to just bite the bullet, and get it done. The fun starts when you get a bad alternator from the parts store!
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Oct 14, 2008
I like having multiple volt meters, I have had them go bad before, read way lower than actual. The battery went dead in my 70S and I wanted to move it. My old 2/10 amp ancient battery charger of Dad's isn't working anymore, my ran over and my free big Schumacher with boost died. My other smaller one with boost died last Summer and I couldn't find my 6 amp mini charger's clamp connection. I use it on the boat batteries which are tied together with the bolt on connection. I decided I needed a proper battery charger with boost. I bought the Dewalt battery charger with a blue light up display. It is very compact and sits under the hood. It has a 24 hour battery conditioner cycle, alternator check function, tells battery percentage, has a 80 amp boost, USB charge port and 6 amp 120V plug in outlet. My point is, you need multiple chargers, meters and tools when you own old cars. Or at least one good one you can trust. The voltage regulator is cheap and easy to change, you just need a paper clip to hold the brushes putting it back together. Your alternator should be 70 amp, which is enough unless you have a big stereo. Buy a charger like the Dewalt and run it through the recondition cycle on your current battery. You also probably need to top up the battery electrolyte levels. Either distilled water or I have been using Vinegar, it is acid, with success. You must be pushing serious voltage to be cooking batteries. It takes weeks or months when a vehicle is around mid 15 volts to boil a battery dry. You need some sort of tester or you are flying blind. Good luck.
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