hi thanks for allowing me into your forum im asking for a freind who has a 60 plate fiesta z tech and his heater is cold he has hot water to the heater after changing thermostat but nothing blowing hotthe fan works ok is there another resistor for the temp control knob he,s replaced the fan resistorwe found a small blue plastic part in the right hand side of the heater case nr clutch pedal and wondered if this had anything to do with it or if its a tamp sensor we are at a loss short of flushing the matrix thruany help would be greatly appreciated thanks again looge.

Many garages now vacuum fill cooling systems these days to help avoid this kind of problem.

With the engine cold or only very slightly warm remove the filler cap remove the filler cap from the expansion tank. Set the heater controls to hot, and start the engine. Let the car idle and reach normal temperature. Air bubbles will make there way out of the expansion tank. Keep topping up the level as required using the coolant (not water). Switch off and replace the cap.

You may have to repeat this process for a few days in order to get all the air out of the system.