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.