Screen demister
Q The demister (DEF) on my 2009 Jaguar X-TYPE 2.0D SE with climate control is not functioning properly. For a while, the demister didn’t work that efficiently, but it has now packed up entirely. The blower motor is running OK and air is coming through the cabin vents, but when you press the ‘Demister’ button, the fan motor carries on running and the light on the button/control illuminates, but hardly any air issues from the screen ducts.
I have checked the cabin filter, which is fine, and cleaned some debris from the filter housing, then run the demister without the filter in place, but it made no difference. I have also checked the F37 blower motor fuse, F39 AC blower motor coil and F49 AC ECU, but these are all OK. I couldn’t reach the F45 air-conditioning ECU as it’s behind the wiring loom. Albert Kirby
A The problem is most likely to be one of the distribution doors in the heater unit plenum chamber which is not correctly positioned, preventing airflow to the top vents. One of the doors may be jammed, but it’s more likely that the actuator which controls the demist door has failed. There are four actuators in all, one on the nearside of the heater box and three on the offside. The demist actuator is the top rear unit on the offside of the heater box nearest to the bulkhead. To access this, you will first need to detach the lower vent that runs above the driver’s footwell. It should then be possible to see the actuator, which is screwed into place.
By removing the actuator, you should be able to operate the door manually to confirm it is free-running. The problem may be either the actuator itself or that the actuator is operating but the spindle has worn and is not gripping the door operating shaft. Alternatively, if you have access to the Jaguar diagnostic system, the operation of the actuators can be checked with this.