85 Plymouth/Dodge Voyager/Caravan charging problem

I've noticed the voltage gauge on the dash is "pulsing" when I use my turn signals. With the engine off the voltage at the battery is 12.7, with the engine running it's 14. The outside temperature is 37 degrees. Do I have an alternator or battery problem? Also, the needle on the gauge is leaning toward the "plus" side a little. Thanks for your help.