The fan works, air conditioning works, but the air wont heat up(knob turns to hot on thermostat). is it a vacuum hose problem, and how do we get to it?

thermostats are always a common culprit for over heating but outer items like poor fin condition on the cores , blocked or partially blocked cores, lack of anti freeze -anti boil coolant, coolant fan not working. timing problems with the ignition, air -fuel ratio not right (too lean) gear selection ( OD not working) fan belt loose. A simple test for a thermostat operation is to start the engine cold and time how long it takes before you can feel hot water in the top radiator hose . 10 minutes at idle would be about right and if you feel the hose start to get hot then the thermostat is opening

If you flushed the coolant with the thermostat in, chances are you didn't flush the coolant. Regardless, it's easiest to check the controls inside first. Does the blower fan work? Does the air flow change from floor to vent, to dash as it's supposed to? Does the A/C change temps when knob is turned from cold to hot? Post results.

Check the vacuum lines to make sure they are correctly connected and in good shape. If they are not, then the system wont move the dampers to allow hot air into the heat vents. A second possibility is a clogged heater core, which is not allowing hot water to circulate through it. As you say the head has been replaced, I would have someone insure every thing was reconnected correctly. It could be the hoses to the heater core are reversed!

fan switch on thermostat housing is bad replace it

you could have an air lock would bleed heater hoses

Make sure the heater hoses are HOT. If they are not real hot then the heater core can be clogged. At that point you can remove both hoses where they go into the firewall and blow compressed air through them or a high pressure water hose until it flows freely. It can also be whats called the blend door actuator. This is an electric motor under the dash that closes a door depending on weather you want heat or a/c. We have seen many times when something has fallen down in the defrost vents and is stuck in the blend door keeping it open partially which would cause a poor heat condition (pens,pencils,etc...) Lastly, if this is a manual a/c system meaning it has a knob for hot to cold-pull the knob off and using needle nose pliars turn the shaft sticking out of the head unit in the direction that would be heat. These knobs are known to round off and lead you to think it is turned all the way, but it's not due to the bad knob. I am confident that one of these is you problem because there just isn't too many components to the heater system and this is what we see on a daily basis. Hope it helps!

I had this problem and noticed a faint clunking sound behind the radio. It was the blend door motor that needed to be replaced. The motor has small fine tooth plastic gears that wear out and won't open to allow heat.

Have you tried replacing the heater core ? If the flushing of the heater core did not work, the heater core may be bad. Very clogged with gunk and residue. did you try to check the valve that opens the hoses to the heater core. This valve can be vacuum, opened by cable or electric. Check to see if the hoses get hot at the firewall. they should be hot.

I would say that it is probably the water pump. I have run into 3 of these on these models this year. They do not overheat however when hooking flow meter up to measure the coolant flow they barely move the meter. Pulled the pump of and found the fins either loose from the pump or the fins worn out.

remove the heater hoses at heater core and backflush heater core with a water hose it is clogged