Having a charging problem with my 2001 F350. The alternator has been charging intermittently with no real rhyme or reason. A few days ago the battery light flickered a bit and then stayed on and the alternator stopped charging. Thinking it was the alternator I bought a new one. When I started the truck after changing it, it was charging normally. About 10 miles down the road the battery light came on, then went off, then on, then off. Messed with everything I could under the hood, changed the (charging relay??) on the pass. side of the valley. Batteries are good and have a good resting voltage. Went through the obvious stuff I could think of and fired the truck up, charging great at full load (everything I could turn on) at idle (14.1v). Shut the truck off and fire it up 20 minutes later and the battery light is on and no charging. I have a feeling it is a ground issue but don't really know where to look. The truck has spent a lot of time off road and on rough dirt roads so there has been a lot of jarring. Sometime the light will cycle off/on a few times while sitting idle.

 

Follow the ground cables off the batteries to the frame/block, remove the grounds clean and try again. IIRC, fuse 27 under dash is for the alternator charging system. Check the fuse for integrity, heck just replace it and make sure it’s snug in the slot.

 

Sounds like something’s loose...as mentioned above, just go around and tighten/clean any connections you see going to the alternator or battery.

 

Decided to put a ground from the battery to the alternator, voltage jumped to 14.6v.

 

This may be a band-aid fix option hiding the original problem. At the very least, your main engine block grounds should be cleaned and test the cables for internal corrosion or degradation.

 

This may be so. The alternator bolts also had a good amount of oxidation on them from the aluminum bracket.

 

This very well may have been your problem all along, although if I recall correctly the alternator mounting bolts thread into the bracket a good 3/4" - 1" which "should" provide more than enough grounding surface, even if only 1 bolt was doing so. An easy way to check is to clean the bolts (if you have not already, inspect the bolt holes for debris or corrosion and then remove the additional grounding strap you just installed.

If your problem has gone away, that was it. If your grounding problem still exists, one of your main ground wires to either side of the engine block may be failing internally.

The reason why I stress making sure the main ground connections are good and secure is because they are very important and if one of the cables is starting to fail, the alternator was your first clue of future problems to come. If the bolts and oxidation on said bolts was your problem, well done on a quick fix.

Let us know what you find.

EDIT: I also installed an additional grounding strap from the alternator bracket to the driver side battery ground terminal when installing the 160A alternator. This was at the same time that I cleaned all existing ground and positive connections as well as adding additional positive cabling.