Citroen XM Forum

The flasher relay is responsible for the ticking sound and the flashing of the turn signals and hazard lights. There may be a separate relay for the left and right sides. Locate the flasher relay(s) in your vehicle and check if they are functioning correctly. You may need to consult your vehicle's manual to find the exact location of the flasher relay(s). The turn signal switch on your steering column may be faulty. If it's not making proper contact, it could cause the issues you're describing. Try moving the turn signal switch back and forth to see if that has any effect on the stuck indicators or hazard lights.

The alarm box on S2 xm isn't behind the radio, its between the blower motor house and heater box, access by removing the lower dash under panel..

This issue is also a common xantia issue, its box lived under the passenger seat. That was known to be a sticky relay inside the box...a swap or relay repair usually solved it.