Batteries not holding charge.

[JCart]

Hey Fellas,
Buddy of mine has a 6.0, batteries keep going flat. So he’s installed new batteries, new alternator still same results. Over 10 hrs they will go flat, nothing left on in the truck, this has just started to happen in the last 2 weeks. I’m not familiar with 6.0 so I’m not sure what this could be. Anything unique to 6.0’s that could manifest in batteries going flat overnight? It’s a 2003, not sure how many kms on it (I never asked him) it’s an automatic. All lights work tranny shifts fine, I wanna say its been ******d but not sure totally on that.
Any info would be most appreciated.
Thanks
J

 

[bismic]

I see you said it was a truck, so I am assuming it is an F-series?

Has it been checked for parasitic current after the engine has been turned off?

Also, the alternator charging is initiated from a voltage signal from the instrument cluster. Is the alternator connector in good shape and same with the connector wiring?

 

[6.0 Tech]

^whs

Especially if there’s an aftermarket stereo system in it. I can’t tell you how many ****ty stereo installs I’ve had to fix for customers. The home of the $1 install tends to cost people a few hundred dollars to fix.

Other than that, I’ve seen clusters, gems, and just random ass shorts cause drains. But I would definitely do a draw test on it to see if there is one, and to isolate it to a specific circuit.


Sent from my iPhone using Tapatalk

 

[JCart]

Thanks for insight fellas,
Went down to jump start it so we could move to location to work on it. It is a 03 SD CCLB 290000 kms. Has aftermarket stereo. Places my heavy duty welding cable jumpers on it drivers side battery to my passenger side battery. I have a 200 amp alternator on my 97 OBS and hooked up my battery said 12.8 volts. His said 11.5 on both batteries. Couldn’t hear the fuel pump kick on, just the vacuum pump I think.
No relays clicking, nor did it fire at all....
Getting it towed to his folks home were we can mess with it tomorrow.
Plan is to charge batteries individually unhooked from truck. Then test for parasitic loss on left side of under dash fuse panel tomorrow.
All I got for now, thanks gain guys appreciate your inputs.
Cheers,
J

 

[bismic]

I would also like to know if the starter solenoid wire under the hood would crank the engine when jumpered to the passenger side battery (+) terminal. With or without the key in the "on" position.

To crank w/ the starter solenoid wire jumpered to battery positive - disconnect starter solenoid wire at the connector along passenger side of engine compartment, and touch on passenger battery positive to crank. It is a yellow wire with light blue striped colored wire adjacent to the passenger side battery in the engine compartment, near the vacuum pump that has a "squeeze-and-pull" type connection.

 

[bismic]

So let me explain the reason for the recommended test.....

You need to know if the starter and the electrical system are working well enough to start. If they are, then you could have an issue that is causing the PCM to NOT send the proper signals (grounds) to the starter relay and/or the fuel pump relay.

The advice in this and the above posts should be a big help to nail down the issue(s).

All we need to see is some action on the above recommendations.