Alt light stays on.

[Rezford70]

I recently changed out my alternator and now the alt light stays on. The battery is reading 12 when it is not running and once started it reads 14.5. So the alternator is charging the batter but I don't know where else to start. I changed out the voltage regulator thinking that may be it but it is still on. Where and what do I do now. Oh the truck is a 1970 ford f100 stick shift. If any one can help please send me some knowledge.

[sublimer]

Continuing from our other discussion...

The alternator could be bad...I know, it's outputting 14.5v and all, but it could still be bad. I've had a "new" alternator be defective before. Take it to a store where they can test them.

Then, quadruple check all of the wiring for the alternator. Then, check it again!

[basketcase0302]

The battery is reading 12 when it is not running and once started it reads 14.5. So the alternator is charging the batter but I don't know where else to start.

Couple of thing to also check. Get a voltage reading at your fuse box, (any fuse) engine running no accessories on. Then take the same reading once you load the alternator, (turn everything on if possible without stalling the engine due to low voltage). Turn on headlights / fan motor / wipers.
This might tell you if your alternator is keeping up with the load or not?
You should still read over 12 volts with everything "cranked" on.
I've never been a big fan of alternator lights. The voltage meter can tell you almost as much with half the issues.

[sublimer]

The battery is reading 12 when it is not running and once started it reads 14.5. So the alternator is charging the batter but I don't know where else to start.

Couple of thing to also check. Get a voltage reading at your fuse box, (any fuse) engine running no accessories on. Then take the same reading once you load the alternator, (turn everything on if possible without stalling the engine due to low voltage). Turn on headlights / fan motor / wipers.
This might tell you if your alternator is keeping up with the load or not?
You should still read over 12 volts with everything "cranked" on.
I've never been a big fan of alternator lights. The voltage meter can tell you almost as much with half the issues.

Good idea basketcase, never thought of reading at the fuse box!

Here's the diagram again with the fusebox near the middle-left...



Depending on your battery, I would change basketcase's statement to, "you should still read around 12 volts with everything "cranked" on." I know I get around 11.8 with my crappy battery. But his point is still valid, if your draw goes below 11 volts, there's still a problem.

[Rezford70]

Ok thanks I will give this a try. I don't know if this would shed some light on the issue, but the other night I drove to the store and when I turned lights on the turn signal lights came on and stayed on in the cab. Well if that helps narrow down the issue let me and thanks for all the suggestions.

[70_F100]

Ok thanks I will give this a try. I don't know if this would shed some light on the issue, but the other night I drove to the store and when I turned lights on the turn signal lights came on and stayed on in the cab. Well if that helps narrow down the issue let me and thanks for all the suggestions.

That sounds like you may have a bad ground somewhere.

[sublimer]

Ok thanks I will give this a try. I don't know if this would shed some light on the issue, but the other night I drove to the store and when I turned lights on the turn signal lights came on and stayed on in the cab. Well if that helps narrow down the issue let me and thanks for all the suggestions.

That sounds like you may have a bad ground somewhere.

In my experience, a bad ground generally cause the light not to come on. I didn't know it was possible for it to keep the light on. The ground is used to complete a circuit, give the electrons a place to flow, hence they can pass through the filament and cause light as they travel to "the ground." How can it keep a light on, I'm curious

I don't intend for my post to seem condescending, I just don't know how, and I love to learn.

[70_F100]

If there's a bad ground, it could be feeding back through one of the filaments in one of the bulbs, thus following the path of least resistance to ground, which could be the instrument panel ground.

[Rezford70]

Ok a faulty ground, ok so how many ground wires does this truck have and where would be the best place to start with trying to get this fixed?

[sublimer]

Ok a faulty ground, ok so how many ground wires does this truck have and where would be the best place to start with trying to get this fixed?

The ground from the battery to the engine block is the first thing to ensure. The alternator also shares the same ground point with the battery if I recall correctly.

[basketcase0302]

There would be a chassis ground up by the DS radiator support to the frame rail.
Another ground from the engine intake manifold to the firewall under the hood.
I believe our fuse box itself also grounds via one of the screw holes?
And your instrument panel has a ground there.