Heater not working - 2006 Land Rover Range Rover Sport

If all the controls are set properly, I'd look for a faulty thermostat as the first choice before looking at more costly fixes.

FIRST, I'd check the engine thermostat to be sure it's closing and allowing the coolant to heat up to a proper temperature. What's the temperature of your engine after five or ten minutes of running? Still showing cold on the gauge? If so, your problem may be as simple as a bad thermostat which can be replaced easily and relatively cheaply. If the thermostat stays open in cold weather, the engine won't heat the coolant properly and you won''t get warm air, plus your engine will lose efficiency and fuel mileage.

If that's not the problem, I'd check the connections where the hoses go to the heater core to be sure they are delivering hot coolant. Then the controls to assure they are opening the heater valve. Also, you could have a plugged heater core. How does the coolant look? Normally it's good for 100K miles but if it looks dirty or really rusty, then you may have a problem. The coolant is a light reddish brown but should not be dark brown. The radiator and heater core may need a profesional flushing.

I hope this helps. Good luck!