My 2007 HHR was towed and went to pick it up in the middle of the night. The next day I notice the horn was not working. And, I could not hear the horn when I would lock the car. They also hit the car and broke a part of the muffler. I went to tell them about the damage, and they said I sign and left so they could not do anything.

does anybody know how he or she disabled the horn and alarm?

 

Probably pulled the fuse or relay or disconnected the battery.

 

The little 5amp fuse in the under hood fuse box