No hot air comes out at all. The air conditioner works fine. air comes through the vent when the unit is off. heater core was bled.

I need more info. When you set the vent control to defrost does it direct the air to the windshield. and when you set it to floor does it go there. if yes the control to divert air is working. before replacing the control unit you need to find the lines that feed hot water to the heater and check to see if line coming in to the heater is hot and the line returning from the heater is warm to hot. sometime the heater gets plug. if so just disconnect the lines to the heater and flow water from your garden hose to the return line of the heater for about a minute or so this will flush dirt from the heater. reattach the lines and check for heat. This is a known problem for all cars as they get old.

the heater core is removable from the climate control unit. The climate contriol unit has to be removed to replace it. The A/C system must be evacuated and lines removed as well as the dash, to access the climate control unit. The steam is coming from a leaking heater core.

The blend air door stuck in cool position

I woild be checking the vent controls as if the ac is working and the core was blocked then the air would be cool when the heat was selected but not changing Fixing the heater has resulted in a /c not being good enough to cool the air if the vent is not properly selecting. The point is that if the vent selection is not working properly (vacuum hoses) then the 2 faults will be related.

if line out is not geting hot then the core must be clogged

vw group products used to have a bleed valve on the top heater hose,to vent any trapped air,now you have to undo the jubilee clip on the top heater hose,ALL vw NEED to be bled after refilling water system.

Scale builds up in the bottom of the heater core. When it gets high enough, it chokes the flow of hot fluid and the fan can only supply cool air. When mine was doing that I disconnected the in and out hoses at the fire wall and flushed it out with garden hose pressure. A lot of junk came out. I reconnected the hoses and bled the air out. It worked good immediately. Two weeks later it happened again. I did repeated the procedure with equal results. It happened again every several weeks for about five or six times, each time lasting a little longer than the last. I guess I need to flush the whole engine out to get all the junk out instead of just the heater core. BTW, the stuff that comes out looks similar to sand if you capture it in a bucket. It sinks to the bottom of the water so you can see it. It must be sinking to the bottom of the heater core, too, and that's why it chokes the flow off.

Sounds like a clogged heater core- insufficient coolant circulating through heater core, and as soon as you blow air past the core, it get cooled off.

heater core is going bad my dodge ram truck did the same thing for about three months then steam startedcoming out of the vents it was antifreeze i have not fixed it yet i just bypassed it for now cause its hot and i have to take the dash completly out to get to it, and yes my airconditioner was blowing out hot now immediatly after i bypassed it blows cold again.you have to find where it goes into the motor on both sides so follow the hoses from firewall then buy a 3ft hose to go from one side of motor to the other problem fixed! well that is you wont have a heater until you change the heater core

Check the actuator motor on the inside of the car on the heater. It shifts the doors of the unit to let the heat and ac shift.