1998 Ranger 3.0 new alternator and battery not charging

[StangerRanger]

1998 Ranger 3.0 - put on new alternator and it is not charging.

But car starts and runs. Dash light for battery is on.

Battery: 12.6v or so

I did the test I saw Ron D Share:

Key Off, B+ to ground on battery: 0v - so a fuse issue?
Key Off, Yellow wire in alternator connector to ground on battery 0v - so a fuse issue ?
Key On, green wire in alternator connector to ground on battery: 12.6 V

In cab fuse panel:
Checked 10 & 11 7.5 amp fuses all were intact.

Under hood fuse panel:
Checked the #4 Mini Fuse and it is not blown but it is a 15a instead of a 30a which is what online diagram for 98 3.0 show. Would that do it?

If maxi fuse was bad would I be able to start truck? Not sure the best way to test the Maxi Fuse but I did locate it.

 

[RonD]

Yes either the B+ wire is broken or MEGA fuse is bad

Test both terminals on the MEGA fuse, both should show 12.6v(battery volts) if only 1 does then fuse is blown replace it

Yellow wire could also have 0 volts if MEGA Fuse is blown

Yes, engine would still start and run with bad MEGA fuse
MEGA fuse isolates alternator from vehicle systems, in case it should produce TOO MANY VOLTS/AMPS which would FRY ALL the electronics in the vehicle, a very bad and costly thing, lol

MEGA fuse should be 175amp
ALT SYS Fuse 30amp, but 15 amp is fine, replace it when you can

Be sure to disconnect 1 battery cable when working on this part of eletric system, or any electric system for that matter, lol

 

[StangerRanger]

@RonD - thank you again for your help and sharing your knowledge. It was the Mega Fuse. Both B+ and Yellow were 0 volts with key off but both had continuity to one side of mega fuse but not across it. Replaced mega fuse for $5.49 and charging system is back to 100%. Hopefully the end of my Ranger troubles for a while.