Battery/charging issues

[Powerstroke]

I have an '05 F350 with the 6.0L diesel. I bought it May of 09. My truck has had a few weak/slow starts in the past but no big deal. It always starts. A couple weeks ago I had an electrical problem that turned out to be a bad ground wire that was rotten and it was replaced. All has seemed fine until thanksgiving week.

I hadn't driven my truck in several days. I used my remote starter to fire up the truck like normal. It started a little slow but it was 6*F outside. When I got in the truck I noticed that the stereo had reset to midnight etc. Since that day the stereo has rest another time and I've had several slow/weak starts. Its never not started, but I'm getting worried. It seems to be better if I plug in the block heater.

So, I grabbed a tester and found 12.6V on the battery after getting home from work. After an hour I checked it again and it was 12.3V. I started the truck with the remote to test the starting drawdown and both batteries dropped to 9.5-9.6V but no further. Once the truck was running and idling, I only get a battery voltage of 11.5V.

Its my understanding that I should be seeing 13-14V once the truck is running. Any thoughts? Is my alternator going out? Both batteries are Walmart batteries and are marked March '09 so they should be good unless they are underrated. I'm sure about that yet. I will check into it.

[Bigtom]

yes you should have a voltage of 13-14 volts. I would unhook the batteries, charge them over night and then test them with a load test just to make sure they are good. You could have a bad cell in the battery. If they test good cheak your alternator if it is chargeing, somthing could be grounded out in it. My best bet it's your alternator. Good luck!

[jeffreyd]

the alt is controlled by the computer. you need to look and see if it has one alt or two. they were putting two on them so one on top and one on the lower side. i dont think they did that in your year but would double check. if your batteries are down chances are you will need to replace them. if one is bad replace them both as the bad one starved the good one and it will soon go bad too.

[fishing tech]

You should have 2 850cca batteries. Walmart batteries suck. Iwas out of town and my wifes battery failed. She got a walmart battery, 3 years later the battery has been replaced 2 times under warranty.

That being said, the radios in that truck have a history of causing draws and drain batteries.

[Scott K]

A couple other things. Do you use the truck for plowing? If so, plow trucks are hard on batteries, and alternators. I would recommend a couple things, first, charge and test both batteries, if bad, replace with the largest cca available in a top name brand. Make sure alt is charging good with a new battery system tester. Then use 10w30 diesel oil in the truck. You will be surprised at how much a difference it will make over 10w40. Next, run the truck at a higher rpm after plowing, dont assume letting it idle will recharge the batteries.

Again, plowing is hard on alternators, an alternator is made to maintain the batteries on normal usage, not to recharge them because of aftermarket add ons that draw huge amperage.

[Powerstroke]

No plowing and the only aftermarket stuff I have is my remote starter. Its functioned fine for the 18months I've owned it. Looks like gonna get the batteries load tested and probably looking for some new batteries.

[spearchucker]

No plowing and the only aftermarket stuff I have is my remote starter. Its functioned fine for the 18months I've owned it. Looks like gonna get the batteries load tested and probably looking for some new batteries.

I would make sure the alternator is fine before putting new batteries in. If you are only seeing 11.5V with the truck running, the alternator doesn't appear to be doing its job.

[BobT]

Does your truck use two batteries connected in parallel? If so, try disconnecting one of the cables that runs between them and check the batteries for charge independently. If one battery is getting weak, it will add a load to the other or possibly be drawing most of the power from your charging system.