Whats does everyones volts reads right after startup?

Mine reads right at 12 for about 30 seconds even with the rpms up a little. Is this normal? After about 30 seconds it rises to about 16.

It's normal.Glowplugs and cranking take a bit of juice.

Mine just stopped doing this, volts go right up, anyone know what happened?

Glow plugs and heat grid pull about 120 Amps on initial start. I would guess if you're not having significant voltage drop upon initial start, your grid may not be working.

Normal operation for volts to drop, especially if the glow plugs are engaged.....also, higher compression, grid heaters, etc..................that's why there's two batteries under the hood, folks.

The LBZ and I believe the LMM use a viscous clutch on the alternator to eliminate the squeek at shutdown. When cold, just like the fan clutch, the fluid needs to warm up. So when you start the truck cold, the alternator clutch is not fully engaged, once the fluid warms up a little bit the alternator clutch engages.