What's up everyone. Haven't posted in a while which has meant no issues w the truck lol. Well today the battery gauge continued to go lower and lower. I had the batt, alt and starter checked. The diagnostic tool said the batt need replaced even thought it read like 12.8 volts. What's weird is the batt indicator on the dash continued to go down which to me would indicate a problem with the alt (charging). Battery is from 09 so I'm gonna replace that and see if it helps but is it possible the gauge connection itself is bad or something?

 

Well.. who and how did they check the battery?

12.8 is good ... IF that is the open circuit "resting" voltage, that is, after any surface charge is removed. That's why it COULD be a defective battery if that is measured right after a drive or charging.

It could also be defective, even if it measures OK and that is an accurate voltage. The conductance type testers are good at weeding these types of failures out.

Typically in a healthy charging system, if one were to measure a battery after a moderate drive (or after charging) it will show an elevated voltage, this isn't the "true" battery voltage. One way to get the actual voltage is wait overnight, say 12 hours or so.

Another is to turn the headlights on (engine OFF) for about 5 minutes or so, then wait for at least 10 minutes. The voltage will "bounce back" to an accurate measurement. What I'm getting at, is 12.8 volts at the battery after a healthy drive isn't good and would indicate a problem. Voltage measurement is an accurate way to determine battery health, actually "state of charge", because a bad battery will usually either stop accepting a charge and/or stop holding one.

Be sure to charge up your new battery as well btw. Brand new batteries are "hard" in terms of accepting a charge and will not reach their full capacity until after several starts. The last new battery I bought took several hours to reach 100%, your alternator will thank you, and this will help ensure maximum battery life too.

 

The truck sputtered when I pulled into my drive. It died but started again and I put it in the garage. Gonna have someone that knows what they are doing look. Some swanky stuff going on electrical wise. Got an ABS light right before I shut it off and it was sputtering getting into the garage

 

Make sure and unhook your battery. If you are having electrical issues like that, don't want to burn down the place! Unhook BOTH positive and negative cables, better safe than sorry!

 

A failing battery can cause some wonky dash indications and lights for sure. I'd get it replaced soon as practicable, assuming that it is in fact defective.

 

I thought you did that already, from your original post. Again who, and how, did they test it?

If they said it's bad after testing, I wouldn't doubt them, considering you're seeing these other related symptoms. But it's super simple and easy to perform your own diagnostics a digital voltmeter can tell practically everything required.

 

I had a shop test it and I watched. It tested the battery, alternator and the starter. It was a handheld digital diagnostic too . The shop was Meineke. All checked out good besides the battery. Maybe I didn't explain but that was done simply because the battery guage has been low lately. However when I got to my driveway the truck started going crazy. Dash lights flashing, sputtering etc. I'm gonna go get a new battery and replace that today and hope if not I can limp to a shop. I sure don't want to have to tow it

 

Yeah, that's what I figured, a new battery should put you in good shape.

 

New battery helped for about 10 min. Then the same. Gauge went lower and lower. I just parked it. Before it died. Weird. Going in the shop

 

Huh. Well I said "should" so I'm covered, ha ha.

Let us know what you find out

 

if you bought a multimeter you could check your alternator yourself, but i have to think that a shop, even a bad one, would be able to do that and, apparently, yours has already done so . the next place i would be looking at is the condition of battery terminals and cables.

 

What voltage was the truck putting out while running?

Did they LOAD test the battery? Or just check voltage?

 

The issue appears to be isolated to when the electric fan kicks on. Reads good on the dash until that draws power then it never comes back up. Wonder if I just need a new bigger alternator?

 

Check your wires? I recently replaced a mishmash of wires with some high end fine stranded big wire I had left from an AV install in my other car. Soldered and sealed all ends. I've had 2 grounds go up over the years.

 

I'd tend to think, that if everything is otherwise OK, a stock OEM alternator should do fine. A larger alternator should not be "required", as such.

One aspect that is sometimes overlooked, as mentioned earlier, run a voltage drop test on the individual battery cables and grounding points and alternator hardware. It's simple, quick and easy, and no disconnecting anything. It's based on the fact that electricity likes to take the easy path.

So if we put a voltmeter in parallel with a wire, or connection, while under load, the voltage drop in that circuit will be displayed as a positive voltage on your DVM. Since an alternator and other high current components will be crippled with ohms resistance practically too small to measure, they are always tested under load, for voltage drop.

Just a few hundredths of an ohm resistance anywhere in the circuit will reduce alternator output by 1/3rd. Maybe not enough to notice at idle, but apply any sort of load, and it will not be able to keep up.

Because of this phenomenon I bet a lot of alternators are replaced unnecessarily. It's not that bigger alternators ain't better but it makes more sense to get the performance we already paid for, instead of heating up wire and spending even more on replacement alternators. Worth checking out anyway.