Hey,

Truck is 96 f150 w/ 351. Recently, the battery warning light in the bottom right corner of the dash has been flickering on and off. Today, while driving back from the gym, it went on and stayed on. What does this light mean? Something I should be concerned about? The gauge is showing over half full (i know these are not very accurate)

Thanks

 

Is your needle bouncing at all, you may need to have your alternator checked out. It could be a bad cable or even the battery. How old is the battery?

 

the ways these work is 90's tech - 1890's...

when you engage the light to the battery (key on, engine off) it lights as it grounds thru the alt. but as the alt comes up to speed the light dims as the voltage differential drops to zero or reverses (battery charge condition)

have the alt tested...

 

I had a 1987 150 and my light kept coming on also. I replaced the alternator 3 times (under warranty, cheaper than just getting a voltage regulator) and it only temporarily fixed it. My truck kept overcharging and my uncle though it to be a good idea to unhook the battery to run on alternator to avoid boiling battery. BAD IDEA. Fried computer. I had to search forever to find a new computer and I replaced the starter relay on firewall and the cable from the relay to the alternator, the problem was fixed. Something in the wire was shorting out or whatever and fried the regulators.

 

Yeah, I know what you mean about uncles, mine burned up my tranny on an 87 cougar XR7 I had. I was adjusting my detent cable on it and had it where I wanted it. Went on a trip out of town, he borrowed the car and unhooked the cable and burned up 3rd and 4th gear, he told me it didn't shift right to him.

 

Thanks everyone. My battery and alternator are not older than 2 years. I went and started it up earlier and the light was on, however I revved it up real quick and the light went off. Turned the truck off for a bit, went out for a drive 5 mins ago and the light was still off..who knows?? Maybe just a sensor?

 

Does your voltage drop when the light comes on?

 

Just to be sure, have you tried to tighten down your battery cables. I'm not an electronic genuis( heck I'm not even a genuis), but I don't think a sensor would turn on the battery light on the dash, though I was proven wrong once already today. Shall we go for 2.

 

the battery cables being loose could cause a problem, but not the light most likely. If the voltage drops when you aren't revving at all your automatic belt tensioner or belt might be going. My F150 had a slippery belt causing me to lose voltage and the ranger had a bad tensioner causing the belt to slip and me to lose voltage

 

My positive cable on my truck broke right where it goes on to the battery and my light came on. Thats the only way I even knew something was wrong. I do however think there is more to it than that, I just don't think it's a sensor.

 

I didn't notice the voltage drop when the light went on, although I only had a 5 minute drive while it was on. Thats why im confused. Im gonna check out the battery terminals and cables tomorrow just to be sure I guess.

 

Something is wrong. The battery cables could be loose or damaged. Battery cables tend to corrode from the inside, so just because they LOOK good doesn't mean that they are.

Batteries can be tested easily at a parts store. You'd be surprised how quickly a batter can crap out when it's ready to give up the ghost. Doesn't matter if it's 2 minutes old or 2 years, they all die.

I'd suspect a cable problem or an issue with the serpentine belt, since revving it "fixed" the problem. I replaced my belt a few months ago because it was squealing and it really brightened up the headlights and the needle stays put with the wipers and lights on.

 

The light comes on when the system voltage is too low (and possibly too high, not sure on that). There's lots of good advice in this thread. It can be a lot of things but the first things to do are to have the alternator and battery tested to try and rule them out.

I had what I thought was a bad diehard battery. Took it back to Sears and they told me it was fine. Turns out that the negative terminal had come loose inside the battery, causing the battery to be bypassed. Lucky for me it didn't fry anything, but disconnecting your battery while the engine is running is a bad idea.

 

yeah don't unplug the battery engine running. when i got in my accident my negative terminal popped off and the truck ran for a good 15 minutes like that and luckily nothing was damaged but it's definitely risky

 

yeah it can!
if it takes 9v to light the light, the battery is 13.2, so thats about 22v the alt would need to put out. you wont notice the light cuz other sh...stuff will be distracting you! ;-)