With my Omega B 2,0 16v Bj. 99 with gas system + ECC the heating is only moderately warm . I already changed the WT (Thank you Kurt Berlin for the good instructions ). The heating now delivers warm air a little earlier , but at minus degrees it is still only moderately warm in the car . It does not matter whether the temperature is at 21° or on HI . Did the engine warm when the heating is switched off and the heating is then switched on the engine temperature goes back . So it can not be in my opinion also the valve . I also synchronized the flaps . Maybe someone has a tip for me . Greeting Achim