Hi Paul
Tore is probably best placed to give you a detailed answer but as nobody has responded yet I'm happy to jump in despite my limited qualifications.
I have recently had a problem where the main heater blower fan in the rear engine compartment was on full blast all of the time when it shouldn't be and having fixed that I do have a better understanding of the heating and ventilation system than I used to.
You don't provide much detail about where your problem resides and there are several fan blowers in the car. So I'm not sure if you are saying some of them are on all of the time or all of them are on all of the time? Also you don't mention whether you have turned the heater temperature up and down and turned the blower speed knob on the CCU up and down. And also when you say it is on all of the time I guess it is only on when you turn the ignition on?
If I was you I would start by reading this page from Tore's website as it gives a great explanation on how the heating and ventilation system should work as well as some fault finding tips.
https://www.bergvillfx.com/categories/964993-hvac-system-details
In short
There is a single fan in the engine compartment which blows the hot air from the engine down a duct to the front of the car
You then have two additional blower fans in the bulkhead of the car on either side to direct the warm or cool air through the vents in the front of the car.
There are also a couple of servo activated valves in the vent system in the footwell on either side. These control the direction of the warm or cool air to the vents around the car.
If you turn the temperature control down to zero and the fan controller to zero none of the three blower fans should be working.
If you leave the temperature control at zero the fan in the rear should still not work but you could then try turning the ccu fan controller knob between 0 and 4 and you should hear the front blower fans speed up or slow down on their four speed settings.
Raising the temperature setting should fire up the fan in the rear to supply the warm air from the engine.
Moving the direction control arrows on the CCU should open and close the servos on the vent flaps to direct the airflow.
If your problem is like mine and the only fan which is stuck on high speed is the one in the rear engine compartment then this is often down to a problem with the relay or the resistor or the temperature sensor. The relay is easy to remove and test and it's under the plastic cover on the inner rear wing next to where the fan resides. The resistor and the temperature sensor are both easy to remove and replace as they just plug into the vent pipe that comes from the blower fan in the rear.
To isolate where your problem resides you can easily stop the fan in the rear by removing the relay or just unplugging the fan from it's power supply - you can see the wire that comes from it and it unplugs easily from a connector. Similarly it's easy to disconnect the two front blowers by removing the relay that controls them - it is in the fuse box under the bonnet.
If none of this fixes your problem or helps you identify it then the issue may be in the CCU control unit itself. In my experience the best way to find this out is to remove the unit from the dash, disconnect the plug from the back, package it up and send it to Tore. He will probably add to this at some stage or correct my suggestions in any event. He is a legend on this stuff!
Good luck and shout if you have any questions that you think I might be able to answer
Marc
