Batt Light

[Eric Powers]

Hi Guys,

I have a 99 Expedition and just replaced the alternator and battery also check all fuses well the garage tested with some probe and replaced a couple. I’m testing 15.89 volts at the battery and also had AutoZone test the charging system and the test says the system is charging the voltage gage reads good any idea why the battery light will not shut off?

Will I be left stranded?

 

[Bedrck47]

what is you voltage reading at the battery with everything turned off and the engine shut off

 

[Eric Powers]

its testing 12.72

 

[Bedrck47]

The Charging System Warning Indicator is ON with the Engine Running (The Battery Voltage Does Not Increase)

A Circuit 35 (O/LB).
A Circuit in-line mini-fuse.
B+ Circuit 36 (Y/W).
B+ mega fuse.
I Circuit 904 (LG/R)
Voltage regulator.
Generator

The System Overcharges (Battery Voltage Greater Than 15.5 Volts)
A Circuit 35 (O/LB).
Generator (low output).
Voltage regulator.
I Circuit 904 (LG/R).

 

[Bedrck47]

start the engine and let it idle then take voltage reading at the battery.

Then run engine to approx. 1500 RPM's and read the battery voltage

 

[Bedrck47]

was this problem happening before you changed the Battery and Alternator??

 

[Eric Powers]

Thursday night the batt light came on then the battery went dead from running the truck.
@ idle 14.89
@ 1.5RPM 14.89

Also I disconnected the battery while the truck was running it didn't stall.

 

[Bedrck47]

check fuse #11 in the battery junction box (under hood fuse box) check it for voltage in and out or pull it and check it with a ohm meter.

 

[Eric Powers]

There isn't a fuse in position 11 there is one in 12. I tried putting a fuse in 11 there isn't any contacts to accept a fuse figuring the garage might of put a fuse in a wrong spot.

 

[Eric Powers]

The test at autozone said the charging system is good. Because the voltage is greater while the truck is running is the battery charging? Can I drive it or will I be stranded?

 

[Bedrck47]

Your output voltage appears to be a little high. According to the wiring diagrams and the owners manual there should be a fuse #11 20 amp for the alternator.

 

[Bedrck47]

Part 1 -How to Test the Alternator (Ford 4.6L, 5.4L).

 

[stamp11127]

Check charging voltage once engine is running with as many systems off as possible. After 15 mins of driving or idling check charging voltage again. The voltage should have dropped. If not the battery will overcharge.
Let us know the readings.
Where did you get the new alternator?