When ever I start my F250, even when hot, the voltage meter starts very low. As I drive the truck and get the revs up, in about 1 minute or so, it comes up. The lights are also dimmer and then as the gauge comes up, so do the lights. Happens during the day as well.

I thought it was the alternator, so, replaced it with a new (not rebuilt) Bosch. Same thing. Like there is a weak line off the alternator or something? Charging works great.. all systems are good and no error codes. Just that low voltage for a minute or so at startup.

Any idea what it could be?

 

I would look at the batteries themselves. You might have one that's weak and dragging the system down. Mine does the same thing, but only when it's really cold and I haven't ran it in a while.

 

It is your glow plugs. They stay on even after the light goes out. They stay on even after the truck starts. They are functioning properly and draw alot of juice. Sorry about the alternator.

 

Thanks... the batteries are pretty new, but I will defiantly check them.

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Ah... that actually sounds right. Its not long after the truck starts and the voltage and gauge come up to normal. I would bet the draw a far amount of juice. And I have a spare alternator now? (Kept the original as well.)

Thanks for the help.

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Here is another post on the issue... and this is the link to a video of the same issue I am having...
Volt meter delay? - Page 3 - Ford Truck Enthusiasts Forums

Guess it it defiantly the cycle of the GP. Thanks again for helping me out!

 

depending how cold the truck is that time should vary, if its not super cold it will only stay down for a few seconds...when its 10 degrees out you will notice they will cycle up to 90 seconds