Just purchased a 56 and I'm new to restoration with beginner knowledge. I have a heater control lever missing (one on the dash plate that sets the heater temperature not the floor to defrost). I can put in a new arm and cable, but how do I know it is not a relay as well I need to purchase? If the heater seems to be putting out heat and defrost, and it does and seems to adjust floor to defrost, to some degree - does that mean the heater relay is OK? If so, I'll just get a lever and cable.