BrooksBier

I have an 87 carrera. I had an Escort radar detector installed and it started powering down saying high voltage. In addtion, I have noticed that my headlights surge sometimes. I had the radar detector read voltage today and it usually reads in the 14 range but did go up to a max of 16.2 volts at one point and was in the 15 range a lot. I know one of the issues with these cars is the alternator and have read that the first sign of them going is overcharging. Does it seem like my alternator is failing? No other symptoms. If it is, should I get a new one that I can get as an upgraded one for about $700 or should I just get an old rebuilt one for a few hundred dollars/

Thank you