Heater fan auto setting

Having an issue with the auto fan control (fan setting on auto not aircon). It works some of the time but most if the time the fan is dead when this position is selected regardless of the temp setting. Fan works as expected manually but heater only seems to blow warm air (not hot or cold). Would it be some control unit? If so any idea where it is and how to fix thanks? 20V turbo. Maybe the internal air thermostat?

If it is the ventilation control unit I need the part number for 20V Turbo (Non aircon) version thanks.

Seems it is very probably the Ventilation Control Unit. Have managed to source one thanks.

I did jump in my Coupe and have a play with this yesterday - I had thought mine only came on with the a/c on.

But no it came on with the a/c on or off and with the heater selector turned up on max, down on cold or anywhere in between.

Re cold air only - from recollection if you have A/c it won't come on if the outside is cold outside- can't recall the ambient temperature off the top of my head. But the sensor is in the drivers side (UK) wing mirror.

Regards

MM

That's right the Auto setting is part of the Heater control and not necessary linked to aircon but I assume if you have aircon it will cool faster if outside temp warmer than inside. I have not got the door sensor as no aircon - have an electronic sunroof instead.
The Auto setting is very useful as if it works it means you don't have to fiddle around with the fan speed all the time. The fan comes on when the engine is warm (if heating) and will come on near max speed until car heated to desired temp then it will idle. If cooling then similar but fan will come on even when engine cold of course. If the control setting the same as outside temp then of course fan fill not come on...so to test it move to extreme hot or cold and fan will come on boost.

Update: It appears the issue is with the internal temp control potentiometer. It is measuring incorrect values. Will replace this asap and hopefully cured!

Update: The potentiometer seems to come with the complete assembly (also fan pot and heater selector control) so had to change the whole board. Now works! The heater pot had gone and the control module then sends air around 22C as it does not know any different. Auto fan now works as well because of this also.

Can anyone supply the part number of the control module as i dont seem to be able to find it on the ePER.

Module part number is 576540600