Luck warm heater

This was discussed recently. General consensus is that modern diesel engines are very efficient at converting fuel to movement. There's not that much heat left over to feed into the cooling system. My Xantia temp gauge stays below the middle sector except when towing a caravan in hot summer temperatures, and even then it only rises just above the centre mark. Selecting a high heater setting when the engine is cold won't make any difference to the maximum warmth achievable. That is limited by the temperature of the coolant around the cylinder head (where it's drawn away to the heater). You could try fitting a higher setting thermostat if available,-most open at about 80C. Ancient remedy you might try is to stick a piece of cardboard or plastic across the lower half of the radiator. Adjust the size until it provides what you want without actually setting the fans off or boiling up. DaveK.

You may have an airlock in the heater circuit leading to poor circulation. There should be some bleed screws to let the air out of varous points in the system ( sorry i don't have a 406 so i don't know where they are located)

Bob

check the inlet pipes to the heater are they hot? if they are then the flap is incorrectly set by the heater ecu if they arent hot then could be thermostat or a blockage

Thanks all. I will investigate

Sy