Hi i have a problem with my f250, i bought 2 new batteries and check the alternator and its fine but i notice it wasnt charging, i dont know whats happening, only charges 12.5v instead of 13.5 or 14v, does the f250 have any alternator fuse? i cant find it please help!!!

 

Welcome to FTE.
Come on over to the 6.0L Power Stroke Diesel - Ford Truck Enthusiasts Forums
Repost the problem and you will find a lot of help.
How are you checking the voltage?
Did you take the alternator in for testing or ?

Sean

 

i test it already in a alternator shop, its working 14v but when i installed it on the truck it only charges 12.5 or 12.3v its not charging... and the batteries are new, i was looking for a alternator fuse or something??

 

does it work when you initially start her up, but then slowly dies off?

I had an issue maybe 4 days ago with my alt. worked great in the morning at initial startup, but after maybe 5 miles voltage dropped to 12-12.5 (ie: battery voltage).

had to take in for testing while burning hot before it would "fail" the test at Oreilleys. $218 later and I have a lifetime warrantied alt...and a new battery because it killed the old suspect one that was previously there. get it fixed soon before it kills your new batteries.


not to mention that your FICM HATES low voltage and it can kill the FICM and injectors

 

wow....when i test the alt in the shop it was cold right and it was 14v at max spin the guy told me the alt was good.... but i dont know why when i put the alt in the engine the voltage is not correct.... 12.3 or 12.5v only it should be 13.5 to 13.9....

 

the alt should be making 13.5+ volts at IDLE. you shouldn't have to spin it up higher than 1,000 RPM to see max voltage output

 

yeah the machine spin it to 1000rpm it show up 14v max

 

The bad thing about the most of the newer machines in the
parts stores is that they are computer operated test and don't
take temp into account when doing a test.
So if you have a unit that is suffering from heat it can test as good.
Some times a diode will test good when cold and as it heats up the junction
will short and pass AC ripple into the DC side.
Here is a little test you can do in the truck


ALTERNATOR - Ripple Voltage Test
Using a DMM
The Alternator produces AC voltage and current. The battery requires DC voltage and current to charge properly. Diodes located within the alternator change (rectify) the AC to DC. However, a small amount of AC can still be present and no harm is done. Problems can develop when alternator diode faults permit unacceptable amounts of AC to pass into the vehicle electrical system.
1. Set the meter to read “AC” Volts (lowest range) .
2. Connect the black COM lead probe tip to the battery negative post.
3. Connect the red Volts lead probe tip to the battery positive post.
4. Run the engine at 1500 RPM.
5. Turn ON the high blower and high beam lights.
6. Your meter reading should not exceed .09 volts (90 mV) AC.
High ripple voltage readings imply faulty diode(s) which can cause:
· Undercharged battery.
· Stalling.
· Rough idle.

NOTE: If your meter reading exceeds 90 mV AC, use an ADL7100 labscope or equivalent to verify that ripple voltage spikes do not exceed one volt peak to peak.

You can find this info at Test - Ripple

There is some more info on that page.

Sean