page CX, BEHR heating unit, level 3 modification:. The heating fan motor (935) (Bosch CPB 2V 23.404) can be swapped by, i.e. a Bosch DPD 2V 3.26.7 double fan motor from a BMW5??. One of the shaft ends (choose the correct one!), must be cut. Cut in the original plastic motor holder with a fixed diameter hole saw. Make a clamp and weld arms to the clamp that fits into the original screw holes. The fan is then pushed onto the shaft and the motor and fan is placed within the fan housing.. 2. The transistor regulator (658) might be upgraded by a M033 (50A darlington). Extra cooling fin should be added to the transistor. The resistor values at the fan control (278) which make up the continuous fan speed regulation might be adjusted to fit the new transistor optimally. 3. (This part actually belongs to the level 2 modification) The plus supply lead to the fan motor should be replaced by a heavy one through a relay. The same applies to the ground lead, running from the full speed relay (745 pin 5), in the consol. Make it short. 4. (Optional:) Remove the consol side cover. Cut a rectangular hole (32x00mm (max)) in the right lower rear corner of the heating unit. The reduced resistant will give an increase in the total flow. As a bonus - when the temperature is set to cold, some warm air will still come to the feet while cold air goes to the screen. To get full effect to the front screen it must be possible to close the rectangular hole. A special duct is under construction.
page 2 The new motor: Bosch DPD 2V 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 2V 23.404. It is faced the opposite way of the DPD motor. The new motor seen from above with the clamp mounted.
page 3 The original fan motor with the plastic 'funnel' and the turbin fan mounted. The four screw holes can be seen at the edge of the plastic. Four small arms that are welded to the clamp which are secured to the motor are fastened here Top view.
page 4 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. Below is an illustration of this clamp with the screws and nuts indicated. The arms has uneven sizes due to the shape of the fan housing.
page 5 This is the original fan regulator transistor and its cooling fin. It might be replaced by the M033 (50A darlington transistor. The location is behind the shelf in the passenger compartment. Boltet to the chassi above the floor mat. At the picture to the right you can see the added extra black cooling fin. It is hot here since the plastic connector shield is often meltet. The same thing is pictured here at top of the table. Though it is an old and coarse picture you may see how the fin is fastened.
page 6 By pulling out the central consol air duct you will see the resistor ladder that is connected to the fan speed wheel on the left side as seen on the picture to the left. This ladder simulate a continuous variable resistance as a control for the transistor regulator. The back of the printed circuit is seen to the left along with a snippet of the schematics as you will find it in the electric documentation, either in Haynes or the original Citroen workshop manual. B V 3B 3B2 Mv 3B3 By using the M033 I think it is not necessarily to do any change to the resistors. 278 3B
page 7 This transistor is close to a direct replacement for the original one and most likely more powerful. It is probably necessary to replace the old one if a bigger motor is mounted. I blew up my original by accident so I have not tested it.
page 8 The Heating Fan Full Speed Relay (745) is located at the right side in the center consol. (Indicated by the red arrow) The schematics is encircled. SInce the F.S.relay(745) has a rather long ground lead it is wise to replace this lead from pin5 with a short heavier one to a nearby ground post. With these arrangements you may easily gain to.5 volt at the motor which makes a big difference. 5N2 R 5N3 745 5N 5N5 5N4 V N G F2 III 6 6B Mv H III 6 6B G H F + 935 Mv 4B B 4B2 B R A relay (R) with a heavy lead from battery +, with a fuse(f) might greatly reduce the voltage loss. Control current to the relay is taken from the plus lead to the fan motor. Q Bl 935, heater blower 5N2 R 5N3 745 5N 5N5 5N4 V N G