I know this is an old thread but closes thing to what I’m experiencing. I’m having a similar issue. 2008 freightliner century with 14L 60 series. So, I have one more issue that I’m trying to figure out. Do you know which wire goes to the plug for the voltage gauge? I’ve tested and cleaned everything (even all grounds). I’m getting the same voltage at the batteries, the jump post, the back of the alternator, and the starter. Usually 14.2 while engine is running and 12.7 while engine is off. But for whatever reason, the voltage gauge reads 9-10 and I have a message on the dash that says warning, low voltage. I’m thinking maybe the wire going to the ecm or dash cluster maybe the culprit. Any help would be greatly appreciated! Thanks