1999 Ford Taurus After Collision

Noises problem
1999 Ford Taurus 170478 miles

I rear ended another driver a few days ago, and since then, my car has been making a loud noise only when my heat/air is on. It sounds sort of like when you put a baseball card a bike tire, but extremely loud and electrical sounding under the hood. The heat and air work fine, it just makes that horrible loud noise, and it goes away once I turn the air/heat off. What could be wrong with it?