the battery/electric guage stays well down below the midpoint, marked "14." After a few seconds it will climb past 14, then fall off again. If I am running the fan, it will surge along with the increase in the guage reading, then fall off again as the guage falls. After I start down the highway, this surging goes away. What is causing it?

 

Your grid heaters are kicking on and off, warming the air so the engine runs a little better at start up. As soon as the truck gets near operating temp, they shut off.

 

nfm**************