01 F-350 Diesel battery light keeps coming on. batteries are good, charging is good, and battery indicator (dash) shows good. Sometimes the truck won't start, other times it acts fine.

Anytime the battery light on the dash comes on is an indicator of the alternator not charging, resulting in a dead battery. Low voltage will cause other warning lights to come on as well. Replace the alternator and fully charge the battery before running the engine, to avoid full field condition with the new alternator ( overheating).

You basically answered your own question. your problem would be the ignition switch.. If you have push button start, this would be different. It would have to go on a scanner to find the problem. Or at least where to start looking.

Does the car crank slowly, or the starter clicks when you attempt to start it? If the alternator or voltage regulator is bad, the battery would continue to lose energy and appear to be bad. Alternators need to be fed voltage since they don't have magnets to excite the windings. On my Volvo, sometimes the indicator lights don't come on when I turn the ignition on, before actually cranking the engine. When this happens, I know from experience that the battery won't charge. Do you get any dash lights showing a problem?

You can check the voltage at the battery when the engine is running; it should be well over 12 volts if charging.

If a trunk, glove compartment or interior light is on, that can run the battery down too.

Hi there,

If the battery dash light remains on, it is a strong indication that you have a recharging issue. The new battery will only work if the alternator keeps it charged well. My suggestion would be to take your car to a mechanic and have your alternator tested.

Good luck.

its best to include a year make and model but it could be a fuel sending unit, bad battery, battery going bad, or something like a bad connection somewhere. also, it would be a good idea to scan for codes at a reputable shop. i will be able to give you more specifics from there.. in the mean time. disconnect both battery cables and charge up your battery. then re install, make sure connections are tight and try to start. let me know what happens.
regards,-tim autoecu1 800-921-9060

is your alternator charging?

Best place to start is the positive lead on the battery . Remove the lead and clean battery pole and terminal using sand paper until you have shiny syrfaces. Replace the lead and tighten the terminal . Check the battery for charge condition as what you describe indicates a flat battery

Check all fuses and verify no melted/damaged wires. You may have damaged something on the charging circuit by reversing the current. The battery light comes on when the alternator is not charging so I would double check the alternator at a different location as it sometimes will show good at one place and bad at another...Also have the battery checked to make sure there was no damage to it in the process and pray that the main fuse blew before any severe damage was caused.

This same thing keeps happening with my car. I've had the battery, alternator, alternator wore and plug changed, and the lights still keep coming on, and car keeps cutting off. I talked to someone today and they said it might be bad wiring or fuses so.... that may be it!

The battery (or IGN) indicator on the dash, when lit, indicates that the alternator is not charging.

Check the battery terminals are not corroded, and the battery +12V and earth connections to the vehicle are in good order.
Check battery electrolyte lvel is ok.

Check the battery terminal voltage - it should be 13.8volts to 14.5 volts with the engine running. Switching on the headlights should not cause any reduction in that voltage while the engine is running.

The battery will not charge significantly unless the terminal voltge is in excess of 13.0V.

If all the above test ok, and the battery discharges between daily vehicle uses you may need a new battery.