O.T. Ford Van Charging/electrical

FIL was given a 92 Econoline by his Sister in law. She put a new battery in it on 5-10-11. It would not keep a charge. She had her son look at it and he said the alternator was bad. I went 80 miles to put a new alternator on it yesterday. I took the old one off and to a parts store. I thought it was expensive, $175 for a rebuilt. I put it on and started it. I let it run and tried to start it again. It barely turned over. We put a battery charger on it for several hours and it still refused to start. We finally jumped it to get it started and I drove it to the farm store where it came from. It died as I was driving thru the door into the service bay. The tech checked it and it only had 9 volts so he replaced it. It would not start so we left it there. It was past closing time. The SIL went there to meet the tow truck and it started for them. They hauled it home. This morning it started so FIL and I went to get it. We saw that the hot battery cable was not clamped tight, so we put a new one on. It started so we headed home. A half mile away we stopped to gas it up. It hesitated starting so we did not shut it off again. When I got home, I let it run. After 5 to 10 minutes it died and would not turn over. I put my battery charger on it and it pegged the meter. As I drove home I had noticed that the volt meter seemed to move down gradually. It was definitely lower when I got home.
Any ideas what to check next? Already new battery and new alternator.
Thanks, Roy

Bad grounds or fusible links are some things to look for.

What is the charging voltage measured at the output of the alternator vs. at the (+) battery terminal?

Had a 91 F250 that was acting close to that. Didn't drive it much so just jumped it when needed. Starter went out later and when I replaced it, the problem went away. Just a thought.


Dave

Fully recharge and test the battery. The alternator is not designed to recharge a dead battery and run all of the electrical accessories. Making the alternator recharge a dead battery is a quick way to fry an alternator. You can check the wires to it: yellow with a white tracer and black with an orange tracer are hot at all times. The white with a black tracer will typically be about 1/2 of battery voltage, and the light green with a red is the signal and warning light circuit. grounding the light green/red wire with the key on will make the warning light come on.
Fully charge the battery and take it along with the alternator to be tested.

Dad always warned me, on a Ford, the battery HAS to be fully charged to test anything! Charge the battery FULLY before starting it again.

Don't a 92 have a separate regulator? I know 91 does, I had 5 of them. Some regulators had connections made of steel and they rusted. On the 91's bad regulator clue was warm alternators on cold mornings without any tools. With engine off if you like your fingers. Dave