Volkswagen: vw passat, engine temperatures, vw passat

Question
heater blows cold air only.


Answer
It could be air trapped in the cooling system, a bad thermostat or a bad water pump.  Any other symptoms like unstable or high or low engine temperatures?  If not, it's most likely that it just needs a bleed.  It could also be that the heater core is plugged, but let's hope it's not that.