I expect to see water on the garage floor after having my car out for a run during the summer. It is now very cold outside, and I have noticed lately that after having my car out for a run (with the heater on) there is water on the garage floor JUST LIKE IN THE SUMMERTIME. Has the HVAC unit lost it's mind? What could be causing this? Is it expensive to fix? (I live 1/2 way between Columbus and Cincinnati Ohio so I know it shouldn't be as expensive as on the East or West coast). Thanks.

You didn't say in what position you had your heater controls in but it sounds like it's in the defrost position. If that is the case when the heater is in defrost the a/c is on to de-humidify the windshield and that moisture your finding on the garage floor is from that.