This may have already been answered somewhere, but I can't seem to find it. I have a 2003 Ford 6.0L Turbo Diesel. About 10 months ago I had the alternator replaced. As soon as the shop replaced it the battery light came on. It would not stay on all the time, it would just come on from time to time. I took it back to the shop and they hooked it a computer said all the codes are fine, the alternator tested at 14.3 and the batteries are good. They said it was a short in the dash for that specific light. (I didn't buy it) The truck ran fine until yesterday when it had trouble starting. I took it back to the shop and again the alternator tested good at 14.3 and the batteries tested fine. Last night, while idleing, the needle on the battery guage kept droping and the lights would dim, then the needle would pop back up, lights would get bright again. When I got home and turned the truck off, it would not restart, it would just click. We put a battery charger on it over night and it started right up this morning. The needle shows it is charging, and when tested the alternator test good at 14.3. Batteries test good at the shop, but the battery light it back on. I am at a loss, can anyone help?

 

replace your batteries and see if that cures it.

 

Mine is doing the exact same thing at the moment. I haven't had trouble starting tho. Battery light would go off once truck got temps up.

 

I would start by checking all of your ground connections to make sure that they are clean and tight, have seen that cause intermittent charging problems in other applications

 

The battery light stays on regardless of engine temp. Yesterday was the first time I had any problems starting the truck. I will check grounds tomorrow. A quick check today didn't uncover any problems, but will admit it was a quick check since it was raining and I was outside

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I was told in another fourm that the battery light would not be on if there is a problem with the batteries, it only comes on if there is a problem with the charging system. Is this true?

 

I dont know about the light and why it comes on but i would do what they said and check all the grounds and wires. ive had issues like this with just one wire corroded. hopefully you find the problem soon goodluck

 

The battery light should come on when the voltage drops below a certain point, im not sure what that setpoint is, its probly around 10-11 volts but not positive. Check and make sure that the plug on the top of the alternator isnt corroded or loose. Do you have dual alternators by chance?

 

Try looking at your voltage through your instrument cluster while you're driving all you have to do is put it in test mode.But i think if your batteries were weak and alternator was bad you would be throwing codes on all your injectors too.

Put your dash in test mode. with your key off press and hold the ODO button on your dash. Now turn your key to run but not starting the engine. the lcd on your dash should say test let go of the button and press the button to get to battery voltage.

 

Dansfordtrk, I only have on alternator.

ArNy64, I did not know I could do that. It took a minute to go through all the read outs but it says the batteries are 12.4/12.5 (it jumps between the two numbers)

 

The best thing to do is take the battery's right out of the truck and take them to your local battery dealer . They will be able to put a proper load on them and see how well they hold 12 volts and how long they hold enough cranking amps under load. They can even test your acid to make sure it is doing its job . You can't tell **** by putting a volt gadge on them even a cheep load tester won't tell you if one or to cells are dead.