My recirculating heater has a cover for the side vent and a handle to change from floor to defrost. No cables. If Grandpa's handle fell off he would have defrost and no heat if the lever was in the defrost position when it broke. But, as red58 posted, the heater must be there to defrost. Are there some hoses to the firewall? You got heater. No hoses? You got cold air drafts. The fan, heater core are all in a sheet metal thing under the glove box, or they are not. Too big to miss.
