i have a question involving my 07. i have factory twin alternators also . when i start up theres about a 30-45 second delay before the alternators tun on ( or the primary to the best of my knowlage) during this " delay " the truck idles and voltage rests at around 11.8. also during this time my FICM voltage is low low .. ive seen it as low as 41.5v eekkkk . ive read that this is caused by the glow plugs staying active causing the voltage to drop , however i can actually hear the motor bog down ( indicating the alts kicking on putting a load on the motor) and then voltage slowly rises . takes about 2 minutes for the FICM to reach 48.5 . i just cant believe the voltage is due to glow plugs. it never did this not once last winter . so heres my questions . .
is my primary alt shot , and the truck just takes a minute or so to realize theres no output from the primary , thus turning on the secondary?
and am i going to f**k up my FICM seeing that low of voltage every time i start the truck?
I've seen high 10s after my truck sits or a few days and almost always high 11s after sitting for a few hours.
FICM sounds dead already.
If you want to increase the voltage at idle do the big 3 wire upgrade and an alternator with a high amperage output at idle. GPs draw up to 250 amps (IIRC) along with all the other stuff radio, AC, lights etc.
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