I have a 98 explorer (centaurus conversion). New starter within last 3 months, and new battery within the last 2. Driving it down the highway today and pressed the horn, all gauges dropped and vehicle slowed. I turned it off and it wouldn't start back up. I jumped it battery held power long enough to get the windows up. Wondering how to distinguish if its wiring or the alternator, or something else?

 

Do you either have or have access to a multimeter?
I not, it's a good investment and not very expensive and also easy to use.

 

just got done testing it, stayed at 13 with lights on and a fully charged battery. Pretty sure its the alternator. Now I'm wondering how to tell if its a belt or the alternator itself.

 

Idle the engine and look under the hood if the alternator spins the belt is ok.

Then take the alternator out and have it tested at the parts store for free. O'Reilly's has better quality re-manufactured alternators than Auto Zone.