Hi, I too have just come across the exact same problem with my heater fan. Unfortuanately I don't have a solution as yet. I have managed to remove the control switches (for air flow, heater and blower control knobs) with the attatched pcb board unit on the rear. I have had the whole unit tested and there doesn't seem to be any problems with it. I - like you, turned my blower onto the auto position and left it there for the remainder of my journey. It wasn't until I drove the car the following day that I noticed that I could no longer control the blower setting or even switch it off! The blower itself seems to be permanently on full power, it's very noisy and annoying. However, I am able to turn the blower switch upto the MAX position, resulting in the increase in power from the blower. It's the only position on the dial that the blower results in any change in power. I have read something about a faulty resistor regarding this problem, on this forum. The chap has mentioned that he bought one from a Citroen Dealer for £10. Don't know where it goes though, or how to get to or even test it. Anyone reading this - please help!!!