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The battery light tells if there is balance in voltage output from the alternator compared to the batteries post. If the engine is not running, the light will be on. The “battery light” is not there to tell you if you have bad batteries, under voltage batteries, fully charged or undercharged. It only tells when there is an alternator output issue, which of course there is if the engine is not running.
Brain isn't working today... Thanks... Was going through your video on the alt/battery light. Voltage looks good on the connector.
On a separate note, what are your thoughts on what is I assume the IC circuit to the alternator causing the cluster to stay on? I assume my other codes were because the IC controls the compass etc and they were powering down and IC was staying on and losing communication?
That video was actually a quick and dirty to get someone here out of trouble.
The I circuit when the alternator is not spinning is a ground circuit, which is why the light comes on. When the alternator is spinning, there is voltage and as it comes up to the same as the batteries through the battery light, the battery light goes off, equal positive voltage each side of the light.
Its an internal high resistance circuit though, about 1.4k ohms for any of our alternators to ground, but it can't back-feed the instrument cluster with positive energy when it's not spinning. Well, unless the voltage regulator or diode packs are really screwed up.
I know this is an old thread but I had the same problem on my 06 f250. I had all the same codes you did, and thanks to your post I figured out my ic errors regarding the charging system. It turns out I unplugged my alternator plug c102a and didnt plug it back in correctly.
It was the jumper wire on the alternator had pulled out of connector (wire 2 on c102a) just enough to not make good connection. It took me 2 weeks and 2 different alternators to figure out what was going on. The wiring diagram says its to the stator.
Hopefully this can help someone who was just as lost as I was. Thank you for your help