I've had it happen several times in our Pontiac Montana. One time, the mouse got hashed in the fan which threw it way out of balance. It was banging on every revolution. I had to pull the fan each time and use a mirror and shop vac to fish the hose through the duct to suck the @#$%^ out.
We had a mouse build a nest in the heater core box on a Dakota my wife used to have. It completely blocked the heater and a/c. That one cost $700 to get out since they had to pull everything out to get at it. Since they already had it apart, we had them put in a new heater core just in case.
