Stupid little red low battery light!

[cbxer55]

So, the little red low battery light keeps coming on intermittently. Yet the volt gauge points dead center, as it should. Yesterday, checked it off and running with a volt gauge. 12.26 off, 14.40 running. Just for giggles, removed the ground in front of the battery and the one on the firewall, cleaned them with a wire brush, reconnected them and squirted them with some battery terminal protectant glop. Light was still glowing when I drove it to work. However, coming home at midnight, it was off. It comes and goes. Sometimes it is on from start-to-stop. Sometimes it is off from start-to-stop. Sometimes it comes on while driving and goes off again.

Do I have a loose wire under the dash that is causing this? Because it starts every time I want it to.

As for the accuracy of the volt gauge: On multiple occasions, it has showed a sharp drop while driving. And when that happens, I just drive to the nearest auto parts store and buy a new battery. Every time it has happened, the battery was tested and found to be bad. So, at least to me, I don't doubt it's accuracy.

Owned this truck 27 years. This is just another of those epic battles it and I have from time-to-time. LOL!!

 

[franklin2]

More than likely one of the small wiring connections to the alternator is dirty or loose. Mess with those and see if the problem goes away. That is where the wire for the light in the dash goes to.

 

[cbxer55]

I'll check it this weekend. Thanks. Funny thing, drove it home last night, no light. Drove it to work today, it was off until the last two miles. Then it started fluttering at first, then came on solid.

 

[Mechrick]

The voltage regulator on the back of the alternator turns that light on. Works like this:

The charge lamp bulb has one side of it connected to battery power all the time. When the key is on, the other side of the bulb is grounded by the voltage regulator. When the truck is started, the regulator applies voltage to the bulb, since there is voltage on both sides of the bulb it goes out. There is also a parallel resistor across the bulb terminals in case the bulb blows. The voltage regulator needs that trickle voltage from the cluster so it can field the alternator.

I would throw a regulator at it, but I always have a few of them laying around.

 

[gw33gp]

I don't trust those battery or charge warnings. The alternator went out in my 02 Ranger a few years ago and I got no warning until the engine started losing power and the tach started acting weird. I made it about two blocks and the engine died. Can say much good about warning lights.

Fortunately, I had a NOCO battery jump starter to power the electronics to get me home.

 

[cbxer55]

One night back in October 2014, returning home from Thunder Valley in Noble Oklahoma, the lights on my Lightning started dimming. Made it home, almost 10 miles. Changed the battery the next day, didn't fix it. Changed the alternator the following day, fixed it. Kept thebattery though, the stock one was 10 years old. That battery, a Sears Platinum AGM battery is still going strong, 11 years later.

I've changed the alternator in the Ranger twice now. I'll check the wires this weekend. Not sure it's the voltage regulator, running it maintains 14.40. Got one of those digital volt gauges that plug into the ciggie outlet.

 

[franklin2]

The voltage regulator on the back of the alternator turns that light on. Works like this:

The charge lamp bulb has one side of it connected to battery power all the time. ...

You meant to say "key on power" not battery power.

 

[bobbywalter]

get a meter on it at the battery and make sure its not over 14.4