I have noticed that every once in a while my guages sweep on start up,as if I just changed the tune or reconected the battery. It has happened in cold and hot weather. It does not happen all the time and it does it when the engine is hot or cold. The truck starts right up and does not groan like the battery is low.

I did relocate the battery last year, ran #1 welding cable.
Alternator is charging about 14.5 volts when running .When off the voltage is about 12.5.

Any ideas?

 

Thats a weird one, that it only does it once in a while. Though mine has done it a few times if the truck sits for a long time with out running.

I would check your grounds.

 

poor/dirty conections, bad/weak battery...mine did this once, replaced with new motorcraft battery and never had any more issues.....

 

mine did it the other day after having the stereo on (pretty loud) for about 20 minutes, and i know my battery is on its last leg

 

Its your battery.

 

battery/battery connections

 

+1 on the battery.

Friend had the exact same symptoms, but as time went on it got more frequent.

Finally replaced the battery - problem has not re-appeared.

I saw your electrical work a while back - I seriously doubt you have any bad connections...