Fan control knob name. Automatic shifter base inner cover name.

When the Automatic Climate Control is set, you are no longer in control of settings and fan speeds. The sensors make the unit run at full speed and don't power down until the set temperature is reached. If you have the temperature set to 18'C (Max Cold), it is likely to never achieve that. If you want to take control back, you need to take it from Auto, to Manual. If it still does it, you need to go to an auto electrician who will use a pro grade scan tool to check on communications to the Body Control Module and the sensors controlling AC, Heating, and Fan Speeds.

This is the Owner Manual covering Climate Control

https://www.manualslib.com/manual/397817/Citroen-C5.html?page=105

This is a technical manual on the D-Series explaining AC, I just found it interesting.

https://www.manualslib.com/manual/1061220/Citroen-Ds-Series.html?page=50#manual

..

Most fan and Ac relays are located in the under hood fuse and relay box. Adequately marked in owners manual or on plastic cover

did you check:'
fuses first then scan the PCM for HVAC errors/ if not you will fail.
the car has


on high only?
key word , only !
as most work only on high if the resistor block fails.

depends on your cars HVAC options,
manual or fancy ,full climate controls.
the FSM covers this.
RTM?
fsm for WJ cars
here
http://colorado4wheel.com/manuals/Jeep/WJ/

and here (has missing pages but is free)

http://www.jeep4x4center.com/knowledge-base/index.htm?utm_source=cj#service

the fan is covered in chapter 24 fully
chapter 10 , automatic zone controls, got that?

if the scan tool has errors, address those first.
the fancy system has 4 computers that work together.
even a blower controller. (brain)

The vehicle is equipped with Automatic Temperature Control, which automatically controls fan speed based upon cabin temperature. Check your user manual for proper operation of the system before proceeding further.
If your fan is stopping before achieving the temperature you set, suspect overheating of the fan relay, a defective fan resistor, or a bad ATC.

The blower and temperature controls are independent if you have the manual system but they are integrated in the control head for the automatic version. The automatic version does not include a set of resistors. Do you know which system you have? If you have manual controls, I recommend you test the resistor with an ohmmeter. It's possible that your blend door actuator and resistor have failed independently. However, if you have the automatic system, your theory is as good as any. By the way, your wiring diagrams are available on autozone.com--they include both manual and automatic system schematics.

Most shifter lighting is not a standard bulb. It's similar to a thin belt that has electronic components. this is located in the shifter itself. Might want to remove the cover and check to see is you can replace the item your self.

yes, jus need to get a booth with a bibig enough base to cover shifter base and get o costom shifter knob from auto shop

Sounds like the fan control knob has shorted out. You can check the fan "blower" relay and fuse in the engine compartment but you need to make sure the control knob is good or you will keep blowing fuses and relays. If your blower fuse and relay are good, then just have the control knob checked and replaced if needed.

there is no computer control unit, what u need to replace is the fan speed control resistor module.

Yes you car has something like a resistor but its called an ATC BLOWER CONTROL MODULE.Its under the dash on the pass side close to the firewall.