1997 ford ranger ,while driving last night my bat gage started to to go toward L .?

the truck eventually stalled and wouldn't restart .My wife came and jumped me and we got it home (drove mostly with lights off) I let the car run in driveway and it started right up this morning and my gage is between H and L.any thoughts i was thinking alternator,but it did however apparently charge the battery when i let it run last night.Could their be a issue with the light draining the battery??

Sounds like a weak alternator that is not putting out the amperage it is supposed to. When you ran it in the driveway you probably had every thing turned off i.e. lights, radio and heat. The alternator is still putting out some current just not enough to support all of those things running at the same time. Go to an auto zone they will test your alternator for free while you wait. I am sure that is your problem it is not your belt or it wouldn't charge at all but that being said i would replace the belt while doing the alternator. You will already have it half way off anyway.

Good luck! Easy Fix

The belt could be slipping at high speed causing the alternator not to charge under load .Or it could be that the alternator is on its way out and that was just a warning. With the car running disconnect the battery negative terminal and see if the car dies if so the alternator is not working if it doesn't die try the same thing with the rpm increased if it dies then the alternator is not working . If it doesn't die then I would look at the battery for a bad cell . Or maybe a direct short on the positive side of the plus cables somewhere.

well after you check belt drive to any parts store or shop have the charging system check most places its free to test and then you know what you need to do it wil be one of either battery belt or alternator easy to have it tested then you dont buy something you dont need.. id go to autozone