I am having the same problem with my 05 berlingo 1.6. I am told it is the "resistor Pack" that has failed on the fan motor. This is slightly confusing given that mine has air con and is controlled by two big power transistors. I'm guessing it refers to the same item. Looking in the manual and talking to my local citroen garage a replacement is required at around £85 plus vat. What concerns me is that they cannot guarantee that this is the actual fault. I have checked the live feed to my fan and it is at battery voltage regardless of what setting the motor is at.
Anyway, if you want to find yours, it lives up behind the glove box. Remove the carpet there and you will see it. 3 M6 screws hold it in place. Hope this helps.
Matt
April 2008