I'll try to make a long story short but it seems like I have to replace my alternator on my 02, 7.3 about every 13 months. Just after they go out of warranty.
I replaced my current one in May of 2012 and this past March, the battery goes dead and I again take it off and was thinking, at least this one is in warranty. The alternator shop puts it on the machine and its charging just fine. He says to check all connections and tells me the voltage that is suppose to be on the plug wires. At least this was an alternator rebuilder and not a general parts house.

I check all connections when I reinstall and it goes to charging just fine. Every so often, the battery idiot light comes on so as to keep a check on it, I wire one of my fluke meters into the cigarette lighter. Then when I found the engine discharging, I could raise the hood, wiggle the plastic plug and it would go to charging again. So I cut the plug off, found some small spade terminals and got a good tight fit. All went well for a while but I noticed that when the idiot light came on and the meter showed discharge, it was mostly in the morning. Seldom in the evenings.

So this morning, for some reason the plug in the cigarette lighter wouldn't work and the light was on all the way to work. Determined to get to the bottom of it, pulled it into my shop bay, raised the hood and put the meter directly on the battery and showed 14 volts. Looked around and the idiot light was on. So the battery voltage shows it's charging but the idiot light and dash voltage shows its not. Now I'm really baffled.

Any thoughts on where the glitch is?

 

I'd replace that CL fuse before going any further, many important things are on that circuit.

 

Now you have lost me. I'm in the marine industry and never heard of a CL fuse. Where is it?

 

i think rich means the "cigarette lighter" , which ever one its on.

 

Duh, and here I was thinking something real secret and techical. Still doesnt' explain why the charging idiot light is blinking while battery voltage is showing charge

 

The OBDII port power is on this, as well as a number of other circuits. Your charge indicator may rely on some obscure device that uses this voltage, so it's always best to have your fuses good before chasing an electrical mystery.

What year is your truck? I need to get the correct charge-circuit diagram.

 

2002 Crew Cab 4WD

 

It is common for the three-connection plug into the alternator to become intermittent.

So much so that the plug is available separately as a replacement part.

Get one, splice it into the wiring harness using solder and shrink-sleeving, and see if that doesn't cure the ills.

If you don't know how to do that wiring job correctly, you will be FAR better-off to have someone competent to do it for you. A car-stereo shop might be a place to start looking for a good electrical tech, but even then, some are so-so at best. Maybe a local ham-radio operator....

Pop

 

We use a female spade terminal in the marine field the same size as the prongs on the alternator so I did solder those on the existing wires and used heat shrink. They be plenty tight and did solve the most of the problem. But the alternator is charging and the batteries is showing a charge. Its the idiot light on the dash that is misleading. So the question is, why is the idiot light on when the alternator is charging? I'm going through the fuse box this afternoon but right now a customer's boat is in the service bay and making money comes first.