Battery or alternator issues?

I WANT ONE

 

Something else you can try .. If you have a VOM (And if you don't, even a cheap-o one from Harbor Freight will work) ....
With everything off ... Check the voltage of the battery. It should be somewhere between 12 - 12.5 volts fully charged. (This is NOT a load test, which should pull a lot of amperage, simulating a starter motor..)
Once the truck is running, check the voltage at the battery posts and it should read approx. 13.8 volts. That means the charging system is working OK. If nothing changed, you got a prob with the alternator, voltage regulator (which now days is built in the computer) or a wiring problem.

 

Great call. Take a quick look at the ground like @wrightme43 said. They do these grounds at the factory over new paint so 3 or 4 years it's not going to be any better. A snowflake washer from the hardware store will always help and ensure the ground is metal to metal. When I was with KIA we would do all the grounds with these before we put a electrical part on the car. 13 of them.
Zim

 

+3 for grounding issues. Find, clean to bare metal on both connections, spray wd-40, or similar to keep water out.

 

I had an issue with a BMW a while back. Started with a radio static and surge. Dead battery one day, charged but would not hold charge overnight. Ended up being a faulty alternator.

I had to argue that both the radio and the battery failed as "consequential damage" resulting from the alternator.

Got everything covered under warranty, even the battery due to the failed alternator that killed it.

 

Is this why the directional signals on BMWs never seem to work?