[MIKEY'S 2002 TA]

hi, i have a 02 trans am. i am having a problem with my voltage once my second radiator fan come s on. i have a new battery and alternator. it charges fine and the volts stay at 14 until that second radiator fan kicks on. then the voltage will steadily keep dropping down to between 10-11 volts. as soon as that fan turns off voltage jumps back to 13-14 volts. i know these fans draw alot of current when they are both on,but the car used to say between 12-13 volts. could it be the fan or the wiring going to the fans??? any input would be appreciated. thanks,mike