Low voltage

10.2? at the low voltage disconnect.

 

I assume you mean the low voltage condition is occurring while the engine is running?

 

A modern Diesel engine with piezo-electric injectors can draw up to 70 amps when running. I wouldn't count on it running for 100 miles.
Could just be bad luck and got a bum alternator. There is an alternator sense fuse, but if that is gone the alternator would have been running over 14.6 volts but it would be worth checking out its only a five amp fuse.

 

First, shut off and/or unplug all unnecessary items. Unfortunately at night, you'll need the headlights...but things such as hvac blower motors, fridge, stereo, interior lights, inverter, etc can be shut off to help get you as far as possible before shutdown. Of course if your cell phone is low, charge that...might need it.

Next opportunity you have, get a digital multi-meter and a test light. Invaluable tools when trying to diagnose electrical issues.

 

It is a electrical disconnect just like it sounds. When it opens you are done untel voltage is restored. I ran a couple old mechanical engines a long way sucked up behind another truck. No headlights, heater-A/C, radio, etc. Don't thank these new ones will do that. If you see a safe place to camp and can get a recharge go after the sun comes up.

 

The fuse is located under the plastic cover on engine side of firewall by steering column.

 

Could be a ground wiring problem. Check the wiring at the batteries and alternator something lose?