interesting, written by Inspector Gadget:

Have been having another slight problem recently with the car recently. The heat setting on the IHKA would only accept hot or cold any other setting would result in boiling hot or freezing cold. I've given advice on this previously but not on this site & should have known better what to do.

The heat in the cabin is measured in various points the main one being a sensor behind a small vent between the drivers side & blower control thumb wheels, this vent and the sensor can get blocked with dust as air is constantly being pulled through by a little veined motor.

Remove the IHKA a quick way is to open the ashtray and pull the unit slightly forward allowing a wide thin bladed impliment to be slid between the IHKA and the centre consoleand lever it forward. This may break a small clip on the side but can be replaced from the dealers for about 30 odd pence.

Once out disconnect the two plugs, if the car has an auto timer on the OBC there are three plugs. Take the unit to a suitable work surface.

Remove the small white plug to the vained motor then undo the 4 screws and remove the backing. The motor can be removed further by unclipping 4 lugs. Clean the motor and plastic air track which will be full of dust.

Next remove three plugs which hold the flywheels in position the unit cannot be further seperated without doing this the plugs have a small clip push it inwards then pull the plug out. Next remove the 5 screws holding the circuit board to the front cover all the switches are attached to this board and will come out complete when the board is removed. Watch you don't loose the little washers from the thumb wheels.

Clean out the vent on the casing and then with contact cleaner clean the temp sensor. I also cleaned the large blue pin connector with contact/electrical cleaner.

Reassemble as removed.

The climate control now works perfectly as do all vents and the difference is like night & day.

There are different problems associated with the heating system, leaking matrix,the sword, the heater valves & aux water pump, stepper motors & broken vent units.