I have noticed recently that my voltage is only 12 amps (stock GM guage) after a cold start and stays this way for 1 to 5 min. and then it jumps up to 14 volts. It only happens after the engine has completely cooled down. Is this normal or should I be concerned.

It's normal... It's the intake heater running (and the glow plugs for a short time).

I thought it was some thing to do with heaters and now I won't have to wast a day at the local dealer. Thanks.

I had the same question awhile ago. You'd think they would put something in the owners manual :banghead: probably save them a few $$$ at the dealers. Did you turn your high idle on yet?

We have had such a mild winter so far that I dont need the high idle.

although its been a mild winter my high idle still kicks in. and man do i love the sound of the turbo when it idles up.

I believe it is the grid heater that draws all the voltage just before start up. The batteries drain a little and then need to be charged back up. It is normal, and all diesels do this. The only exception is if you plug the truck in, then it starts up and you will not see the lower voltage on the gauge. There are already a few threads on this, do a search and you will find them. The situation is discussed at length.