Hello,
I have recently purchased a 77' Electra Limited with 49,000 original miles. Everything seems to work with the exception of the heater. Correction, the heater works great, it will not stop working. The system is turned "Off" however it will continue to blow hot air out of the lower vents? Anyone have any advice as to the culprit? Thanks-

 

Welcome to the forum! In a car of that age, there can be a few things causing the problem. It might be in the heater controls itself, or in the actuators that control where the air goes (they have a technical name that escapes me right now..)

 

Temperature vent door actuator is the newer cars. Most the older 60's-80's fleet cars and trucks I driven had similar issue where it felt like the heat from the engine bay is coming in. Maintenance department told us it was normal. Were you able to put it on recirculate and see if the heat still comes in?