Some info
Is the car climate control?
Do you have fan operation?
Do you have vent control operation?
Stick your head under the dash on the drivers side and look to the middle of the dash...see a rod and a little white or black thing with two small hoses on it????
Move the heater controls....Does the bar move?
Does the cam the bar is attached to move?
Pull one of the small line of the white or black switch of, do you get a vacuum (car running)? If not pull the other one of and try it.
If you get a vacuum at the hose reconnect it to the switch and see if you get a vacuum at the switch where the other hose would be connected?
If so move the heater controls and see if the vacuum stops.
If not replace vacuum switch.
If so check that the heater tap (drivers side near inner guard, two or four heater hoses connected) and make sure the little arm moves when you move the heater controls from cold to hot. Also make sure that there is not a zippy tie holding it closed.
If this is OK then let the car cool and pull the hoses off of the heater tap and fluch through the heater core via the hoses going into the firewall. Water Flow???
Failing this you have a bigger problem!!! Get back to us and let us know how you went with the above and I'll do some more thinking!!
Regards Guy.