Batt dash light came on 3 times but for 10 seconds each time

It's a S-10 v-6 vortec 4.3 liter motor 4 X 4 crew cab and all is fine but on the hi-way about 60 - 75 I get the battery light come on for a few seconds 3 differnt times I have a new belt,water pump, upper & lower hoses just recently done but it did this thing once before I had the work done so weird can the ALTERNATOR be on it's way out and how can I tell if its the original alternator the truck has 137,777 miles on it so it may be when the light came on I looked at the voltage and it was at 14 volts so I dont if I would see a surge on the gauge right away real time ? like it would say 10 volts or lower thank you very much for the help

Could be a loose connection at the alternator or battery, could be a failing alternator, or the belt tensioner could be weak causing the belt to slip. Most auto parts stores will check the alternator for you. Don't settle for the "off car" testers, it's much better to test it while it's bolted on and the entire system can be tested.