Charging issues

Hey all.

My battery light came on yesterday morning so I rushed back home. The voltage was dropping rapidly so I shut the truck down.

I dropped the battery off at NAPA to be tested.

Meanwhile, I checked all the connections and cleaned things up.

The battery came back Good, so I reinstalled it and the truck was working fine again. I assumed it must've just been poor/rusted connections.

I drove around all day yesterday and most of today, but then this evening the battery light came on again and I rushed back home.

It will only start when boosted and as soon as I disconnect the cables, the voltage drops rapidly. There is magnetism at the pulley as well as the positive bolt on the alternator.

Is it normal for a failing alternator to work intermittently like that? Is there anything else I should test before replacing the alternator?

Thanks

 

How many miles? Could be just worn out brushes, but it would be good to see if the battery is charging at all with the engine running by checking with a multimeter.

 

242 miles. Not sure if it's the original alternator or not.

It does charge when connected to another vehicle. As soon as I disconnect, it starts rapidly losing voltage.

https://imgur.com/a/vY8QCH4

 

I might actually just rip it out tomorrow and check the brushes.

 

I had the same issue and tracked it down to wire chafing. It was the bundle of wires that go down the drivers side firewall from the fuse box. I’m not near my truck now or I’d take a photo. The insulation was rubbed off several of the wires, and the wire in one was mostly broken. Spliced it back together and has been working perfectly since.

 

I bet that was fun to diagnose... I have 12v on the alternator bolt as well as the pins in the connector so I'm hoping it isn't a wiring issue.

 

I had a similar issue, my alternator started throwing high amps and blowing out headlights (fun for driving at night). Put a new/remanufactured alternator in. Only takes 30-45 minutes to install.