I have a 1995 3500 dually 12 valve. It seem to take a long time befor it starts charging, some times the check engine light comes on. My frist diesel can someone help.

 

What's the temperature been when you've noticed this?

It is fall, and the nights are getting colder, and thus the cold morning starts.

Takes a while for the heater grid to stop needing juice, so the alternator guage will sit low for a while.


phox

 

It does it when it's hot or cold.

 

Bad charging diode?

 

Does the tach work properly when the alt is acting up?? The computer controls power to alt to make it start chargeing. Do the key on/off/on/off/leave on trick and count the flashes of the check engine light.

There will be at least a code 55 which means self test is done. See what it says and go from there. But probably just the brushes getting worn in the alt. You can always take it off and have it tested at the parts place.