The transistor pack has gone open circuit, drop the heater blower motor out & replace the transistor pack, it sits inside the blower motor.
Or scrapyard & hunt through the pile of Peugeot / Citroen stuff for a good second hand blower motor.
Unplug the blower motor / pull the fuse or relay because if you leave it you will start to burn the wiring loom out at the relays connector plug.
Lee, July 2007