I have a 06 f350 batteries going dead during start up no battery light when you turn the key batteries are new alternator rebuilt and tested some times no charging could come from the exciter wire or battery light

 

I haven't looked at mine, so this might not apply, but is the field winding getting power? No field winding power = no alternator output

 

time for a new...or a warranty claim on the rebuilt alternator.

 

The alternator is charging most of the time. Some time between when the glow plugs come on with no charge then back off. there is not enough voltage at batteries to the exciter wire to open up the regulator so it will start charging. Should battery light come on when the key is turned on. Bc i have no battery light.

 

How many volts are at your battery when the truck is off, and what does it measure when the truck is running? Were the batteries fully charged before trying to start?

Those glow plugs suck a lot of juice, so if the batteries were weak to begin with, they'll just flatten the battery a lot sooner.

 

glow plugs will also stay on for up to 2 minutes after you start the truck....

 

yes batteries have 12.8 v the charge light does not come on when the ignition is on all other warning lights come on taking dash apart to get two battery warning light to see why it does not come on rebuilt alternator and tested!!! batteries charged and tested
exciter wire maybe sorted some of the time please respond

 

If you change batteries, change both, do not just change one. Your batteries are only as good as the "worst" one.

 

does anyone know were the green and red strip wire from the alternator go