My voltage is fluctuating between 12.5 and 13.25. I took it to Ford day before yesterday and they could not find anything wrong. I never get even close to 14 or more. This is the 4th alternator that I know of and this one is OEM. Any suggestions?
disconnect your batteries and clean all the grounds, and connections to the alternator/starter etc. The 6.0Ls have a severely underrated charging system. Long story short 4 batteries, an alternator, and a FICM before I really understood the issue lol.
I would get each battery tested when not connected to the truck, take your alternator off (takes 5 minutes as you probably know) test it off the truck. Check the battery and wire connections.
Not likely you have a bad alternator but on the 4th one something else is going on.
How and when are you checking your voltage? If from the OBDII port mine reads about 0.5V lower than the batteries, and if your checking when the glow plugs are still cycling (first 2 minutes when cold) 12.5 sounds about right
The voltage on my 03 7.3 Excursion stays rock solid all of the time. On my 05 6.0 Excursion, it bounces around constantly from 13-13.8v. I was wondering if it was just my truck. Maybe not. Stays rock solid from the alternator to the input on the fuse box. But drops from the input to the OBD port.
Brand new batteries and new alternator and all new 2/0 custom battery cables and grounds.
I was checking about through the obd fart and the gauge on my pillar. I had one of my mechanics check the alternator and batteries and they all checked fine the alternator was putting out about a half of a more than what the other gauges show. And he suggested checking on my ground connections. He also said that the 6.0s are notoriously low on voltage output
If cables and connections test good it won’t hurt to add a high quality ground strap or two. The nice stainless braided ones look factory. Or make some from batter cables.
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