For several days, we were hearing scratching coming from the floor vent in the kitchen near the garage door. Jeff was sure it was a little mouse that had squeezed in under the door (there is a very tiny crack) and had dropped down into the vent and gotten stuck in there. He had eluded several traps and Jeff kept getting more and more mouse traps and setting them up in the kitchen in big elaborate patterns hoping to eventually catch the little creature.
About a week into the ordeal, Jeff went into the basement storage space and was face to face with a full grown squirrel. The squirrel was frightened and jumped into the HVA/C unit which is what we had been hearing. This is what had been causing all of the ruckus. We bought a raccoon trap and finally captured the squirrel and released him back into the wild (the backyard).