The dot matrix display to the left of the steering wheel of the Series II is known to develop an annoying fault: missing pixel columns. Being rather unsightly to look at, this might sometimes completely ruin our enjoyment of the all too common ABS OUT OF USE readout. :-)
The XM has a couple of billion electrical parts. It's not always easy to find where a specific item is located.
The factory manual and the circuit diagrams denote every part with a reference number. The listing below uses these numbers. Left and right, as usual, refers to the driving position.
Non-obvious parts in the XM
53 Water temperature control unit - LHD: Remove the glovebox. The unit is housed in a black Bitron box attached to the firewall side of the opening. RHD: The unit is located above the accelerator pedal.
The ECU operates three electrovalves to switch the suspension between hard (default) and soft modes. There are three parts involved in this operation:
Although there is a so-called repair kit for the brake valve, this only contains replacement rubber seals. These seal the valve to the outside but they have nothing to do with the functioning of the valve itself; the sealing of the working elements rely on the very close tolerance between those parts. Once the pistons inside the valve or the cylinder they travel in wear out, the valve starts leaking (this means leakage into its return lines and not to the outside world).
Before you disconnect the battery on a Hydractive I XM, never forget to wait for the system to release the pressure. If you fail to observe this, serious damage can occur the next time the system is started.
When you retrofit items not originally fitted to your car, you often have to tap into wires or make new connections not already present in the electrical circuitry. The best way to do that is by soldering. Although making nice soldered joints requires a little bit of training and experience, it's still far from rocket science. Practice here doesn't mean months or years, much more like five minutes, especially as we're not speaking about soldering delicate semiconductor components on multilayer printed circuit boards but a couple of thick wires...
Avoid silicone based products, they are rather harmful, although it might seem different at first sight.
The long hydrocarbon chains that make up the rubber of the tires are attacked by both ultraviolet rays and ozone. As the molecules break up, the rubber loses its elasticity. The manufacturers use carbon black to protect the rubber against UV rays (this is why we only have black tires). A wax based protector is also used: as the tire rolls on the road, additional wax is forced to the surface and absorbes the harmful effects of ozone.
Follow the instructions in the Comments column.
With all those various spheres and damper diameter holes, for any given Citroën model or even accross models, it is difficult to see at first how and why all these physical factors influence the suspension comfort.
The XM came equipped with one of two possible power steering systems. The conventional one is practically equivalent to the BX one, with sizes of cylinders adjusted for proper assistance force. This is called DIRASS from the French Direction Asistée. The other is the self-centering, speed sensitive, fully amplified system to be found on the SM and the CX as well, called DIRAVI (Direction Appel Rasservi) or, sometimes, Varipower. This system is completely different from the conventional one, even the supporting hydraulic components are different.