1997 12valve
Im 500 miles from home in a hotel room.
GEN light just came on a few miles before I got to hotel.
Its dark and raining and I have some limited tools with me. No multimeter unfortunately.
Im not sure if the rain has anything to do with it but I've never seen the GEN light come on before.
I cant do anything tonight but If I start it up in the morning and the GEN light is still on, what can I check?

 

The most common cause is the brushes in the alternator getting worn out. If you catch it early enough, it's usually just a matter of replacing the brushes and polishing up the slip rings. however, if it goes long enough to stop charging, the slip rings might be chewed up enough to warrant a replacement alternator, especially if you are away from home.

Of course, it's possible that the problem is something else- a failure of the voltage regulator circuit in the PCM, a wiring problem, or a blown charge fuse for whatever reason.

 

Find an AutoZone, or other big name parts place. Almost all of them now carry their own diagnostic equipment, and test for free. Stop at harbor freight, and buy a multimeter. Cost you under $20. Keep it in your truck for future issues.