Hey Guys,

I have a 94 F150, 4.9 I6, E4OD with 142,000 miles on it. I have a question about the activity of the battery/alternator gauge on this truck. Actually, the first question that I have is, what is the name of that gauge???

Now, for the real question:

When I am driving the truck, the needle on this particular gauge is right in the middle; straight up and down. I notice, however, that when I stop the truck at a light (especially at night when driving with headlights), that the gauge begins to indicate a weakness in this system. It still stays in the "NORMAL" range, but it is closer towards the "N" or the "O", as opposed to being right around the "M."

The interior dash lights dim, the turn signal will slow and I can notice the beams from my headlights dim, as well. As soon as I accellerate away from the light, the gauge centers itself (back to dead center), the blinker speeds up, the lights become brighter, etc...

I would imagine that this is indicative of either a weak battery, or alternator. I was hoping that someone could explain to me what is happening so that I can learn about this, and understand what is happening here.

I really appreciate you guys taking the time to read this, and thank you all in advance for whatever help you can give.

Garry Baker

 

You could have a bad alternator-- Alternators are basically 3 phase AC generators with a pair of diodes on each phase to convert the AC to 14+Volts DC. One of the 3 pair of diodes can go bad. The alternator will continue to charge at speed but can not keep up at idle and you will get the symptoms you describe. The other and more likely is that you have a bad cell in the battery or an old battery that doesn't hold a charge very well due to sulfating of the plates.. A load test of the battery will confirm this. When running the alternator holds the load, so the gage reads OK. Usually a battery with a bad cell will show only 10-12 or so volts when sitting (no input from the alternator), the voltage will drop rapidly with a load and no input.
You could also have bad battery cables/ends. Check the cables and battery post condition for corrosion or a loose or poor connection at both ends. Your local auto parts store, like Autozone , can test the battery and alternator.

 

Thanks for the input, and I welcome any and all.

I have no issues replacing the alternator and the battery altogether. At least then I will know that it was done right, that the parts are new, and that those two things are two less things that I will have to worry about.

Again, I appreciate your taking the time to explain this to me. Long live FTE!!!

Garry Baker

 

a kwik compuker scan my tell other things