Have changed thermostats (even works). Filling up water has worked reasonably well, only now no warm air comes out of the heater. Is there a trick how to vent the heater or what do I have to do? Is a passat year 89. with 1.6er 72hp no climate (was probably not also for the engine) Someone an idea? P.S.Bin has already driven about 50 km but no heating