69 road runner with factory A/C? When I press the switch to turn on the heat (or defrost), the A/C compressor clutch engages and I get cold air. What is wrong.

Many cars run the AC comp on defrost to keep the seals lubed and for moister in the air. But the air blows through the evaporator and then the heater core so if you have cold air on defrost it sounds like you are just not getting heat which means no hot water through the heater core or the blend door is not working right. Does it get hot at all on heat ? Ron

Not all the pushbutton (yellowish plastic) are the same even though a lot of sellers advertise them that way. A switch with the part number 3501126 is for a C body and turns the compressor on with buttons 3, 4, & 5.