Yesterday I noticed my battery gauge fluctuating between the usual position of halfway between the two extremes (high/low) and about 1/4 of the way up from the low end. It wasn't really acting up or anything so I just wanted to know if the gauge is a dummy gauge or if this might be an actual problem? I've been having excess corrosion on my battery terminals for some time now but I've never noticed this fluctuation before. I'm hesitant to believe the battery is failing because as of two weeks ago, that little green light was still present. Any thoughts?

 

Well lots of corrosion on the batery posts would suggest to me things like the battery is near the end of it's life, or it's being overcharged, or maybe it has a failing cell.

The green eye hydometer, only monitors the condition of one cell, not the condition of all the cells in the battery.

All that said, I'd run this ride by your favorite autoparts store, like Advance Auto, AutoZone, ect, for a no cost electrical system check up via their portable electrical system tester.

It can properly load test the battery & alternator in the vehicle & will likely sniff out any problems in the battery cables, battery, alternator, or its regulator.

Let us know what you find.

 

Yesterday I forgot to locate the nearest AutoZone before leaving work, so I didn't go. This morning it was raining. My windshield wipers were excruciatingly sluggish (luckily I had applied Rain-X a few weeks ago!), the lights were dim inside AND out, and the battery gauge was nearly at the "low" indicator. All of the sudden as I was about to get off the freeway, full power was restored and things worked well again. After the first stoplight, however, it went back to the low power conditions. Bad main ground? Someone at work just suggested that to me. Either way, I'm checking out AutoZone at lunchtime, provided it stops raining...

 

With the problem suddenly clearing up, then coming back, and your report of corrosion in your initial post, it sounds like a loose electrical connection somewhere.

Could be battery cables, their connection points at the battery (loose & corroded), or the ground point to the engine, or a alternator electrical connection problem, or a internal problem with the alternator itself.

With the voltage drop this bad, you should be having slow cranking problems with the starter motor, as it requires a lot of current from the battery on a cold start.

What ever it is, I'd get it checked out & put right, rain or no rain before getting back on the freeway. If that puppy decides to lay down on you at the wrong time...... well you know what could happen!!!!

 

Update... it got worse Friday night but I managed to make it home to my tools... then the battery completely died. I decided to get an Optima battery and I bought a couple of new cables. After I exchanged the battery for the right one (Thanks, Autozone...) I took the truck back to another parts store to have them test it. The guy there said it showed no power from the alternator and since I already did some testing on it yesterday, I decided to just get a new alternator and install it right now. So that's what's I'm doing. A couple of things I learned...
1.) Apparently, Ford advises that you put a plastic bag over your alternator if you're going to power wash your engine. My dad thought we should power wash my engine a few weeks ago... sans bag.
2.) The new alternator says not to try using it with a less-than-full battery.
Now we'll see if this is the problem.

 

It seems that everything is working just fine now! I'm going to take the alternator to the store and have them check it to make sure it was the problem and get back the core charge. I'll update when I finish!

 

I would guess that the battery cables are toasted.

 

In a lot of cases, intermittent charging is due to warn brushes in the alternator.

 

Well, I had the guys at the parts store throw my old alternator on their tester and they said it was indeed bad. My truck is actually running a little better than it used to! The headlights used to be really dim and it was difficult to see the road in the dark. A friend was driving with me and noticed the difference in brightness! And this may not be due to the repair/replace, but it seems that my truck now accelerates better. Perhaps it wanted to relearn its idle better? Thanks to all who left suggestions!

 

OK, good find fix & feedback D-ranged.

Better to take the time to use those no cost diagnostics to find the root cause, than just throw parts at a problem.

Good to hear all is well now & it's running better.

Low or intermittent alternator output puts extra strain on the entire electical system, from having to operate a lower than designed voltage.

So things like the battery, fuel pump, injectors, coil, spark plugs, MAF, O2, computer, ect, aren't up to prime operating conditions, sorta sluggish & it can cause them to operate hotter than normal too!!!!

So, I'd check the batteries state of charge & electrolyte level & top off with distilled water, if needed.
If it needs re-charging, do it with a automatic battery charger set on a low rate, say 6 amps or less & let it slowly come back to full charge.

If the charge is really down, DON'T drive the vehicle to let the alternator recharge the battery, as this will overwork the new alterntor & overcharge the battey at a higher than needed amp rate, such that the electrolyte can boil, & uncover the plates & the heat from high amps can warp the plates!!!!

The alterntor isn't desiged to completely recharge a rundown battery & if run at a high rate of charge amps for a extended time, can over heat & damage it!!!