Hot air comes thru defrost vents and floor vents. Can't seem to stop it. What needs to be replaced? Someone suggested a vacuum line leak. Any hints on where to begin? For what its worth the fan speed selector switch and blower motor still work correctly.
Look on your firewall and you should see a small nipple for a vacuum hose. You'll have to find that nipple and also the vacuum hose that goes on it.
If not in the engine compartment, check for the inside of the vacuum connector where it connects to the connector, driver's side under the dash.