Rough running when cold out

[bartle00]

When it's cold old side and it's been sitting over night and I start it up; it will start, but all my lights are dimming and my battery gauge fluctuates. I have a CD player that shows my voltage for the battery and it can drop down as low as 10.3 volts and then goes back up and down until the truck warms up and then it is better, but not perfect. It is fine in temps at about 25 degrees and up, but when it get colder it gets really rough. Then while that is happening and I try to drive my headlights and tail lights dim down almost like they are not on.
-my dad is a mechanic and he says it's not the battery or an alternator. He thinks it is something behind the instrument panel. We think it is a short somewhere. Can you help us out with this?

Any help with this would be greatly appreciated!

[TahoeFever]

sounds like a bad ground somewhere usually after a few years the grounds start to corrode and get week...
if you got headlights dimming and stuff then you really got a bad ground or a bad connection start with the cables in the block then work your way up

usally with a bad short the truck will just quit out on yah all together .