69 lincoln mark 3. After the car has warmed up.The defogger and deicer blow cold air. The vacuum line going to the heater control valve in the engine compartment has no suction on it. The only way to get the heater to blow hot air is if I hook up a vacuum pump to the heater control valve suck it down for a minute. Once I release the vacuum the and leave the vacuum line off of the heater control valve the temperature in car increases from 60 degrees to 120 degrees. Not sure what the problem is?