I have an odd battery light problem and I am kinda wondering if just maybe my alternator is starting to go bad in spite of testing OK. What happens is that about 2 or 3 minutes after starting and then taking off driving, the battery light will come on for about 45-50 seconds and then go out. This happens only occasionally and NOT every time I drive it. Maybe brushes or brush contact starting to go bad? If it would just stay on, I could trouble shoot it, but it goes away too quickly. Both batteries are new and they seem to stay nicely charged ANd the voltage at the batts is 13.96 so it seems that the alternator is putting out OK---at least when I check it. Truck is an 2007 F250 Superduty 6.0 Diesel with about 91700 miles on it...shows no "dimming lights", no other indications of low batts or no charge at all pretty much ever...got me scratching my head as it seems to me to be too low mileage for the alternator to be going bad, but I dunno!!

Has anyone had this intermittent battery light problem (NOT just a "flicker") and, if so, what did it turn out to be and what cured it? Comments, experiences or ideas anyone???

 

I had it happen on my 99 f250. Its a 5.4l though. My light would come and go as it pleased but everything was charging great. I took it off and had it tested twice. Finally took it to an alternator/starter rebuild shop and they tore it down. Found one of the brushes wore a groove in the stator and would make the light come on. A new alternator fixed my problem.

 

Also had the same thing happen in a buddies mustang. Seems to be a common occurrence.

 

 

OK..so you think that the voltage showing just a tad over .6 volts less (14.6 minus 13.94) could be significant. Maybe I'll have the alternator checked again. I had it checked about two weeks ago and the tester they used was only a PASS or FAIL unit and it didn't show actual measured voltage. My digital (and who knows how accurate it may be) it shows 00.00 with the two leads shorted together) shows 13.96 +/- a few hundredths.

 

13.94 volts is perfectly fine. You may well have a alt. going bad, but you do NOT want to see 14.6 volts or higher. Do you know which alt. you have? A stock 110 amp would have a hard time getting to 13.94v., even a 140 amp would be hard pressed. I have a 230 amp Leece Neville with an overdrive pulley that sits between 13.9 and 14.2 volts and I would start to worry if it started to put out 14.6 v. or higher other than an occasional burst.

 

Yeah..it is the stocker.....I think it is 110 amps. Now that it seems to be possibly going south on me, I'm thinking about taking it out (will probably throw it in the back to have as a spare if needed) and installing a higher amp rated alternator in its place------I just haven't made up my mind which one yet, but I don't think I'll ever consume over 200 amps, so I'm thinking that maybe 180 or 190 would do the job.....not to mention I don't want to spen more money that I reasonably need to...I'm a cheap old fart.

 

Hard to beat the Leece Neville for the money.

 

I'm having the same issue on a 2009 F450 6.4 Powerstroke. The battery light will sometimes come on when starting the engine and then go off after 40-45 seconds. I can also turn the engine off and restart and the light won't come back on. I had an engine fire in September caused by the lower alternator. The dealership replaced both alternators as part of the repair. I never had a battery light before these repairs. The dealer has checked the alternators, batteries, wiring connections and found nothing wrong. There were not even any codes they could pull from the computer. I'm thinking of adding a voltage meter on the dash so I can monitor the batteries and see if there is a significant drop off when the battery light comes on.