Battery light flashes; batteries seem fine

[Old Skool]

My battery light has been flashing in my 90 F250 7.3L. Though I haven't officially checked the batteries, my truck seems to crank and fire within seconds of turning the ignition. This is a New To Me truck and I'm new to 7.3's as well. Is this a common minor issue with these trucks or is there a possibility that one of my batteries is dying and the other one is pulling most the power? Thanks!

 

[subway]

your alternator might be on its way out, its not really a common problem to just have a battery light flicker. you can do a quick test is to check the batteries voltage after they have been sitting for a bit to give up a residual charge that might give a false high reading. let them sit at least a few hours after the truck has been running and you should have at least 12.5 volts.

if it is to low your batteries are worn or your alt is not doing its job.

to check the alternator quickly you should start your truck and let it idle. you should see 13.5-14.5 volts at the battery. turn on your lights and whatever else and with a load you should not have less than 13.5 volts at the batteries.

might also be a good time to check over your battery cables and the conditions of them overall. check the ends and how well they are connected to the battery and block. some bad connections can cause issues as well.

 

[Old Skool]

Just noticed while at lunch that the light doesn't flicker all the time. Hardly ever when I'm sitting still, only when I'm driving.

 

[f350flatbed]

I have the same problem with the battery light. My entire battery cable set needs to be replaced, though. I am going to work on that this week.

Paul

 

[LSOSGT1109]

Mine flashes every now and then. I have no idea why. Batteries are new, alternator tests fine and the cables are in good shape. So I pay no attention to it.

 

[FORDMAN41291]

its a bad + connection probably on ur battery. I had the same problem took me forever to figure it out... check the battery connections and all + connections..

 

[Black dawg]

my truck has done this a few times over the years, usually just crappy connection at the voltage regulator.

 

[Kevin 007]

Up to 1991 there was a little black rectangle plug on the top or sid of the alternator that doesn't ever fit perfectly snug; and when its loose or wiggling around the battery light comes on. Make sure it is fitting snug and im betting that light will go out. Iv'e had 3 idi's do this.

 

[FORDMAN41291]

black_dawg and kevin are both right it also could be the voltage regulator, could be a wire on the regulator or the regulator itself, but most likely a loose wire.

 

[f350flatbed]

Nice tip about the loose connector. Mine does that and I'll check it out tomorrow. I unhooked all the battery connections and cleaned them all up and put them back together and it still does it, so I'll try the connector.

Paul