heated seats not working 04 silverado
 

so here is the deal i have a 04 silverado 1500., had the stock mirrors on there and heated seats worked and everything. recently just bought towing mirrors for my truck that have heat,power, and signal. During install didn't unplug negative terminal from battery like said. Now after mirrors are installed my heated seats have started to act up. the lights will come on indicating that the seats are turned on but that after a little while they just shut off on their own. Not sure what the issue is whether its a fuse or something to do with the mirrors that i put on. I NEED THIS FIXED!!! cold up here in minnesota