Need help electrical issues!!!!!!!
 

I had a new windshield installed today on 01 SS when I picked it up I opened the door and there was a busing noise coming from pass side fuse panel seems like one of the relays. When I shut the door and start engine the constant noise goes to a buss every 10 sec. I ask an employee about it and he said it start when they plugged the rear view mirror in. The owner was't there and while driving home I noticed a noise under the hood and it sounds like it was the rad. fan and also the temp.gauge is not working. I called a mechanic and he told me to try unhooking the battery for 10 to 15 min. I did and I still have the problem. Anyone have an idea what may be going on? Thanks Steve