Voltage issue

Alternator

 

Either something electrical is failing and has an inordinately high draw, or the alternator is tired. Check your fuses and breakers. A hot one would point to a problem somewhere in the system that might explain the voltage drop, or it’s time for an alternator.

 

The high draw may be the ecm. Should know pretty soon if it fries the fuse and quits altogether. Have them plug into it and take them for a rip, if the ecm is on the way out they should see it in the real-time data on the road.

 

If they didn’t check it on the road with the engine running under load, they didn’t check it. It may be ok key on not running or at idle, but go all to #### when the function load drives the draw up.

 

Have them test the alternator itself. Make sure it's putting out the volts and do a amperage draw.

Have them test the volts at the batteries with EVERYTHING on.

I don't think shops do those tests anymore.

 

Computer says there’s nothing wrong when something obviously is. Just can’t wait for them to get those computer driven trucks going. Must be a population control program or they’d never consider such foolishness.