Thread: Alt breaker

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My brother has a F250 that he has replaced 4 alternators on trying to fix this issue.
It charges for about 30 minutes then the breaker trips and it stops charging and runs off the Battery, till the truck finally dies. The thing is he had a new cab put on the truck and this is when this stuff started to happen. He had found a wire the guy didn't connect to the alternator and connected it to see if that would fix the problem, but it is doing the same thing. I said, it sounds like something is back feeding to me. Then I asked if he noticed anything else that seem'd different or that had changed??? He said his dash lights stay on all the time now which they didn't before. Then he said after about 20 minutes or so that his Neg, cable on his battery is getting hot. I said well I know something is back feeding now if the Neg cable is getting hot. He said the Alt, is hooked up, right so do you think it could be the dash light switch back feeding some how and causing the Alt breaker to trip??? Any help or help with what you guys think!!! Thanks for any input guys. Kind of hard to guess what it might be when he is in Ohio and I am out in or near Vegas. Something back feeding is tripping that Alternator breaker though. Thanks again.

There are multiple dedicated ground straps between the cab and the chassis on Ford trucks (maybe others too?). My grandson has a 2005 F150 that his dad bought new, and his dash lights started doing funny things. They found that the body mount for a ground strap had rusted out, and connecting a good ground fixed it. That one was behind the passenger kick panel, a ground strap from above that bolted to a ground near the bottom of the cab where a rust pocket had formed, eating away the body and leaving the ground strap hanging loose.

I'd say whoever did the cab swap ignored the ground straps, thinking they were redundant, or that the cab mounting bolts were all the ground it needs. Check out the factory wiring diagram, and make sure that all of the cab grounds are connected.

Ditto what Roger said, If the ground wire is getting hot, it is not a good ground, add another wire from battery ground to block and then from there to body. Crawl around underneath and find / verify all the grounds!

maybe the battery ground strap is too small

And to add, when I say "verify" the grounds, I mean remove the fastener and make sure there is no paint or corrosion between the connections.