2008 does use Fusible links
3 of them in a 4.0l, 2 in a 2.3l Ranger
So lets test voltage at alternator
KEY OFF
Test battery volts, FIRST, so you have a reference voltage
Ground volt meter to Alternator's metal case for all tests
Test voltage on the B+ terminal, the bigger wire, back of alternator, stud/nut terminal, should be Battery Volts EXACTLY
If not 1 fusible link is bad, and that effects the next test
Unplug the 2 or 3 wire Voltage regulator plug on the alternator
Test the Red wire(2008), should be battery volts EXACTLY, if not, and B+ was battery volts, then a different fusible link is bad
Test Gray wire(2008), should be 0 volts
Turn on key
Gray wire should now be close to battery volts, this one doesn't have to be exact
And that's it
If these 3 wires test OK then plug back in the connector and start engine
Test battery voltage again
Should be 14volt or higher, if not alternator is bad, PERIOD, don't care if "it tests OK" at parts store, or if its the 3rd "new" alternator, its bad if the 3 wires were good
Fusible links are INSIDE wiring harness wrapped up usually
Look at engine fuse box, should see TWO red wires going into it, one is from a battery positive terminal, the OTHER Red wire goes to the fusible link in the wiring harness so start to unwrap it at that end
When you find it there will be a SPLICE with 1 or 2 other fusible links
Diagram below