I figured I would ask you experts before a dump a bunch of cash.

Here is the quick background. Truck battery light coming on maybe 5-10 seconds after up and running and then shuts off typically don't see it again. Last night the returning from a short trip the battery light comes on solid and doesn't go off. The radio freaks out, ABS light come and goes and everything is dim. I stopped at Autozone and had them check the alternator while the truck was running and it was at 8 volts. Except for the rest of the short drive home I was confident the alternator was out as the voltage was low while running. I pulled it off and sent the wife to Autozone and the alternator tests good. I didn't believe it so I pulled out both batteries and took the alternator to O'rileys and both batterys test bad but the alternator is testing good. Now I am not sure what they actually test on these type of tests but is it possible just the batteries are bad and the alternator is really good? Why didn't I see the higher (12-14V) reading while it was running?

Unless I get a better idea from one of you, the plan it to take the alternator to an altenator/starter shop and have them look at it. A 600 dollar repair this time of the year isn't making me too happy with only 40K miles. What do you all think? 06 F-250 6.0L with 40K miles and no mods.

 

Yes the batterys can wear out,glowplugs and alot of short trips will kill the batterys in a couple years for sure.The GPs and 18-1 compression make the 6.0L hard on the charging system if it is used for short hops around town.I suspect the ground is loose on your truck from how you decribe it.Check the ground wire on the passengers side front bottom of the block.It might be loose or corroded.But it could just be the batterys are toast,replace them with the best you can afford, interstate is very good value for the money IMHO.

 

Sounds like you have a couple of shorted cells and that is like throwing a high resistance ground at your alternator. The flickering could have been caused by the batteries also.

 

Based on the two responses I have seen (THANK YOU), it sounds like I should replace only the batteries and see where that gets me.

 

As Brickie also stated check all your grounds and esp. the exciter wire on the back of the alternator. It is also a known trouble spot.

 

...and don't be surprised after replacing the batteries that within a month or two that you will replace the alternator......

 

Picked up some 850 CCA Interstate batteries. I will check all connections listed above. I appreciate all the feedback.

Thanks,
Stoney

PS. How do you add the signature with the truck information to your posts?

 

I have occasionally had the Battery Light flicker.

It tends to happen if truck has been sitting a few days or been on short trips that drains the battery.

My hypothesis is heavy current / or bad cells in one or both batteries...

However, in my case, the light does not stay on.. only flicker and goes away.

Alternator was new as of last year.

 

Good choice. Now keep a sharp eye on that alternator. It's very common for the bad batteries to take out the alternator.

You need at least 25 posts, and about a 24 hour delay, before you can build a "signature". Once the option is turned on for you, you will find it in the USER CP.

Welcome to FTE!!!

 

New batteries back in. Alternator back on. 12.7 volts on both batteries with everything off. With truck running I have 14.2V per the DC volt meter across both batteries (checked each battery not across them in series). I checked all cables and found nothing that looked corroded and nothing was loose. Hope the problem is fixed and I will make sure to check the output of the alternator in the future.

I truely appreciate all the help.

Stoney

 

The batteries are in parallel

 

Your right. I simply meant I did them both seperately.

 

Update:

Drove the truck the day after and the battery light flickered on and off a couple of times and then went off for good. The truck sat for two days and then pulled the race trailer to the track. Battery light came on about 1/2 way there ~30 minutes and stayed on until I shut the truck off. Next day on the way home same thing.

Replaced the alt and drove it to work this morning ~35-40 minutes, no battery light. Hope I have it now!!!

 

Oh.... I am going to do an extended post about this in a bit....

I had the battery light come on intermittently (and goes off just as quickly).

Also had instrument panel lights not all light... etc.

Fix tried: R&R instrument panel... remove all bulbs.. clean contacts of bulb sockets AND also wiring harness connections with circuit cleaner.

Will try to do the other end it 2 harness plug into as well.

So far...

All problems gone.

 

Have a 2005 6.0L diesel with approximately 195K miles. Noticed the low voltage warning light flickering in instrument panel. To resolve problem, replaced both batteries, soldered new battery end fittings, on positive and ground on both batteries, replaced alternator and serpentine belt. Still, after drive truck for 10-15 minutes, low voltage indicator light comes on (flickers) As push on accelerator pedal, to increase speed, low voltage indicator light comes on and flickers. Have checked voltage output, via cigarette lighter, notice voltage level does drop below 12V when low voltage indicator light in dash comes on. Again the low voltage indicator light flickers when try to (softly) accelerate. When mash on accelerator pedal hard (to floor) or left off accelerator pedal, low voltage indicator light goes off. Not sure what to do to resolve low voltage issue?