I am having problems with my 94 F-150 XLT, 5.0efi, 4x4.
Was having problems starting her due to a dead battery. Replaced battery (Die-Hard, silver) and she started again. Then, after about two weeks, this battery died so I replaced the altenator.
Through all of this I noticed that when;
The engine was warmed up and driven (>15 mins), and, lights on, and at a stop, (worse with turn signals) the dashboard voltage gauge would drop towards the low end and often bounce there.
After futher driving this will get worse and even the red battery light will come on.
The tach shows that she is idleing okay.
As soon as I accelerate away from the stop, the gauge moves back to normal and the light goes out.
I now have random mornings of not starting and having to throw a charger on to get to work.
Codes are all normal. (111)
I assumed a short and found the trailer harness wire plug was very corroded, (Minnesota winters mean salt), but even after disconnecting this, my problem remains.
I can find no other shorts by visual inspection.