The cabin heater is not controlling. When ignition is turned on it all works perfectly, howver when I start the engine there is a temperature differential between the passenger side and the driver side. Both get hotter as the car engine warms up and the engine accelerates. The heater control valve has been replaced twice, the second time by a Jaguar dealership. I've checked the air intake flaps and they are all working ok. Any helpful suggestions would be appreciated.