had alternator replaced due to high voltage warning msg on dash. doing it again on 2002 Volvo V70 XC

alternator was replaced with new one a week ago for high voltage msg on info in dash also battery light comes on and heater fan will cut on and off seams to happen more on take off over 1000 rpm brake light and abs light will also flash on at times you can cut the engine off and restart and lights go off have confirmed that voltage does go up off 17 volts any idea whats wrong

Asked by for the 2002 Volvo V70 XC