Out of the blue, my f250 lost charge in the batteries this weekend. I replaced the cranking battery and was able and the problem seem to be resolved. I got the truck back to my house and noticed that the voltage meter was slowly leaking down and bottomed out. The truck would still run but, immediately after shutting off, the new battery was dead.
Will the alternator cause this? or do I have something more serious. I am not familiar with how the dual battery system works. Also, if it is the alternator, how do I know if I have the Single system, or the dual system that the autoparts store keeps asking about?
Ok, let me run this by you as well. I could take the positive terminal off the left side battery which is new which the truck kept running. I took the positive terminal of the 2nd battery (right side) standing in front of truck and the truck shut off immediately.
I know normally this would point to the alternator on a single battery system.
What do you think?
Take both batteries out of the truck at the same time and have them load tested.
The batteries are connected in parallel, so you should be able to disconnect either one while running, and the truck will stay running. Both batteries act as a SINGLE battery, just twice as powerful. To effectively "take the battery out", BOTH must be removed at the same time.
At the age of your truck, I would suspect that maybe your alternator brushes are worn beyond service limits, and the alternator isn't doing as good a job keeping the batteries charged as it might otherwise.
As suggested above, however, it could be simply worn out batteries. If so, replace the pair, not just one.
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