As most CX owner has experienced, the heater fan does not deliver enough air flow either in hot or cold climate. I initially mounted an extra blower and an extra heater matrix (see other pictures). Though it helped it took the space of the spare wheel and was as such a little awkward. Currently it is removed.
Instead I replaced the heater fan motor with a more powerful motor. This motor was initially meant for a BMW(518?). This replacing involves cutting in the old motor retainer and making a new retainer to keep the motor in place.
During my Eberspächer installation I blew up the transistorized fan regulator. I got a new one that could cope with the new motor with good margin. This, maybe, led to a need for revitalizing of the resistor line that make up the variable speed.
Now it gives more airflow, but there's still room for improvment. One could be to rewire the full speed leads with a heavier wire.

This picture shows the transistor with its cooling fins. The MJ15004, PNP, TO-3, 20A, 140 Volt have got an extra cooling fin on top to be sure it could keep up the new more powerful Bosch motor. The resistor at the transistors base has been changed to 5 Ohm.

Conponent side of the heater fan control circuit board. Seven resistors illude a smooth regulator.

List of old resistors from lower right and left-right-left-right..: 2K, 270, 130, 510, 390, 1,1K, 820

List of new resistors: 1K, 18, 18, 22, 10, 180, 47

The printed circuits copper side.
The white plastic with sliding contacts is moved up and down by a lever on the regulator wheel. When it's moved fully down it the sliding contacts activate the full speed relay.

The board is seen here mounted to the console duct section, engaged to the regulator wheel and coupled to the system by the white connector at the lower end.

The transistor unit is in its test position. At the passengers side, just below the place where it is located normally. It is laying upon the glove trunk.

The unit is bolted onto the chassis, under the dashboard, above the glove trunk in the passengers compartment.

The new motor: Bosch DPD 12V 3.26.7 with the turbin fan mounted. The shaft, protruding left -down has to be cut. The other motor is the original: Bosch CPB 12V 23.404. It is faced the opposite way of the DPD motor.

A clamp was made from 8x4mm iron and an old CX door hinge bolt cut into pieces and welded to the two halfs. A little bolt and a nut to tighten it onto the motor. Four small arms was welded to this clamp. The arms rests on, and are screwed with the original screws to the fan housing and this holds the motor in a steady grip.

The clamp is mounted on the new motor. The original plastic motor retainer is cut to let the bigger motor slip through. This plastic is retained to keep the 'air dynamics' intact.

The 'surgeon' himself in the 'laboratory'. Has put on goggles and the gown and tries to look serious. :-)

A simple sketch of the clamp that holds the new motor to the heater housing by means of a four small arms that are welded to the clamp. These arms are fastened to the housing by the original screws.