So, this morning I get in my truck, and it wont start. Tried to turn over for a second or two, and stopped. Noticed the glow plug indicator wont go out. Seems like low voltage to me. I jumped it with my wifes car, and it fired right up. Had Torque Pro running, Alternate output was good, went for a ride, its output % was 30-50% for a few minutes but then settled down to 10-15% which is normal it seems.

I replaced both batt's 18 months ago with Autozone Platinum AGM's. So I run over to Autozone and ask them to test them, and of course they come back 100% charged, and alternator putting out 14.4 volts while running. And he says "no problem"

I asked the clerk if we needed to remove at least one of the ground wires from one of the batteries to isolate them for the load test? He says no, not necessary. I guess I'm not buying that, but wanted to verify with you guys. I'm thinking I've got a bad battery, and will go back there (with a wrench to disconnect myself) and have them test again if needed.

What do you guys think? If I need to go to the dealer so be it, just want to rule out something simple like batteries before I do that though. There are no codes, or dash lights indicating a problem.

 

Batteries have to be isolated from each other during a load test or the results are invalid. Disconnect the gnd. from one battery, test it, reconnect and do the same for the other battery. That way you don't lose all of your presets.

 

thanks CJ. I should just be able to remove negative from one of the batteries, and then they are both isolated from each other, right? I don't think there is a need to do it to both, even separately. Just trying to minimize the time the autozone guy has to stand there waiting for me.

 

I would pull the battery and bench test it. Then the other.

 

Thanks Scott. I dont have a load tester at my disposal. I will just disconnect them both. no biggie losing the settings, and a system reset might be healthy anyway.

 

and of course that begs the second question. in the event that one of them is bad. At 18 months old, do I spring for a new second battery, or stick with it? Problem just started today.

 

My Ford dealer tested my batteries with both connected, then I explained how it really should be done. He had no clue.

All you need to do is remove one cable from one battery, then test each battery.

 

Assuming 1 battery went bad today I would think replacing the 1 bad battery would be sufficient since they're both relatively new.

 

Had one AutoZone go bad early and they replaced both free of charge since it's a diesel. You may have to ask for the manager but they did that for me twice when I had my 6.0.

 

Thanks all, for the feedback. I will go back to autozone soon, and retest. I have not had a reoccurrence yet though, either. Truck is sitting for a week while I am out of town, so hopefully it will start at the airport....

 

Well, as it turns out, I needed a jump after the truck sat for a week. Went straight to autozone, had to explain once again to the clerk(a different one) that he needed to disconnect negative terminal on one of the batteries. Turned out the passenger side batt was the problem. they initially were not going to replace it without doing the "required" put it on the charger for a couple of hours. I asked him, how that would work, and if he expected me to sit there at the store that entire time. He said, no just come back..... He couldn't seem to grasp that the truck needs both batteries to start/run. I told him that if he couldn't do the warranty swap right now, that I would just pay for it and be on my way. He relented, and did the swap.