Ok...I am going to copy my posts from another forum and see if anyone here can help me.

In the last 5 years I have put 4 alternators on my truck. Original alt. lasted 5 or 6 years then went bad. I replaced it with a Kragen brand, it went bad with-in a couple months. Someone mentioned stay away from them. So I got a NAPA alt. and it went bad with-in a few months. NAPA suggested to put a motorcraft alt on, so I did threw NAPA. The motorcraft alt. lasted 2 months shy of two years. Good thing it had a two year warr. I replaced it with another Motorcraft alt. The alt. is charging but the battery light is still on.

Yes the wires are installed right.

Someone mentioned these year alt's. have problems with the built in regulator?

Could someone tell me what is going on? Why do I keep loosing alt's.? Why is my alt. charging and light still on.


The alternators were working for a few months, when I noticed the battery light come on I checked it with my volt meter to see if it was working. The alternator I have now shows it charging but the battery light is still on. I have had this alt. on sence Aug. The light came on not long after replacing the alt. So far as the batteries, My truck starts up normal as if the batteries were fully charged. I guess I could or should have them load tested.
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The alternators that I replaced were definitely bad.

The first thing I check when I have a battery go dead is the alternator.

Anyways, I disconnected both batteries to see how many volts were in each, both 12 volts.

Next step...Load test each battery

I will let everyone know the outcome as soon as I do it. It might be a couple days. I live out in the country and sometimes work long days. So I will do it when I can.


Ok.....I went and had my batteries tested, both were fine. One the cranking amps were a little lower than the other. (old batteries were dated 05/06).

So I decided to replace them both anyways. (new ones dated 01/12)

Battery light is still on.

With the truck running (old and new batteries) the alt. is putting out 14.2 volts (seems a little high). The two wires coming out of the back of the alternator connector is at 12.2 volts running or turned off.

I am thinking replace the alternator.....anymore suggestions.


Ok......I just went and played with it a little more. I check for dirty wires etc. I cleaned them all up. I decided to pull the wire connector with the two wires off the back of the alternator. With the connector unpluged I crossed the wires with a volt meter, it read 12.2 I then started the truck up with the connector unpluged the batt. light was off. I pluged the connector back into the alt. and the light came back on.

I thought this should be opposite.....pluged in light off.....unpluged light on


tenpack, Could you tell me how to do a voltage drop on the output wire. I ran the volt meter from the big wire to the battery. It was putting out 14.2 volts




So....The battery light is on.

I have two new batteries. I am charging at both batteries 14.2v. All connections are clean.

Why is my battery light still on?
One thing I didnt mention is my alternator gets real hot to the touch.