I have a 1984 B250 van with a 360 engine. The battery kept ending up dead so I changed it, same problem. So naturally I changed the altenator expecting it to solve the problem, It didn't. Still ending up with the same problem. I charge the battery, drive a few days, then It won't crank over, even after I just shut it off. Any Ideas would be welcome, thanks.

 

You either got a bum alternator or your voltage regulator is no good.

 

The voltage regulator can look fine and have soaked up some water. You wont know until you take it off the firewall.

 

I had the same problem with an 87 b150 with a slant 6. Ended up being a bad wire tucked behind the power brake booster. The alternator was putting out 14v but the battery never saw it.

 

i have the same van and same problem. my new battery is taller than my old one, resulting in the negative terminal touching the hood when closed. i am assuming that the paint on the hood buffered the contact points for awhile, but since it has now worn down to bare metal, is draining or shorting something. i try the cheapest fix first, ill let you know when i find out more.

 

The negative cable and post touching the hood is not the power lost problem. If the positive cable touched the hood then you would have a very nasty short.

The problem as stated above is one generaly three problems
1) battery
2) alternator
3) voltage regulator

It can also be a bad wire, either the field wire or the battery charging wire

If in doubt about the alternator then remove it and have it tested. If battery and alternator test good then replace the regulator.

NOTE: If your battery charge is low and you want the longest life possible from it recharge it on the lowest amp setting on your charger you can. You may need to leave it to recharge overnight. Fast charging a low battery will overheat it and shorten its exspected life. I have sadly seen several batterys boiled to death from people trying to fast charge them.