Its on a 2004 f 250 and im wondering if anything can affect the voltage. i check it key on 48 volts crank it 47 volt when it first starts it drops to 36 volt and then when i drive it jumps back up to 47 volts. what do you guys think i should do.

 

What are the volts at idle?

 

Check it again on a cold motor. It shouldn't be dropping at all. How does the truck start/run?

 

the truck starts and runs good the rpms jump alittle sometimes but other wise no problem. the motor is cold. i get the readings when i first start it in the morning. and then after i drive it 1 mile or so it jumps up form 36 volts to 47 volts.

 

So its at 36v after you first start it? Pretty sure its going out.

 

That or maybe you have a charging issue somewhere which isn't allowing it to get up to 48V right away. It should be 48V the entire time. How old are the batteries? I'd have those load tested first, and then have the alternator tested too.

 

When my FICM dropped below 48 volts it cost me injector #2... Easy to fix if you pull it up on youtube.

 

Mine stays between 47-48