Help! Was driving earlier today and had the heat on and it was working/blowing great. All of the sudden I heard a slam/bang and the heat just quit blowing out. I instantly thought that the blower locked up and drove home. Started doing some investigating and the blower still works on all speeds just no air at all. I took the duct work off the bottom of the heater box and the flap is open; I can see the heater core and it's clean, no blockage at all. Maybe the thud/slam sound was a door being slammed shut from lost vacuum?

 

First year and model of the vehicle would help. Second check your vacuum lines.

 

'66 442, factory air.

 

The squirrelcage fan has probably come off of the blower motor shaft, which was the noise you heard. I've had this happen to me before. The only other option is that one of the vacuum actuators that control airflow inside the HVAC box has failed and the flapper door snapped shut.

 

You're right Joe, fan was sitting there in 2 parts. Prior owner tried to JB weld it back together and obviously didn't hold. Off to shop for a wheel.