2011 C4GP - extreme fan noise

Dear C4 owners,

last week I bought myself (and the family; two 18 months old twin girls and wife who is 36 weeks pregnant) a C4GP. My previous car was a 2006 C4, so I stayed loyal to the Citroen C4

I have read through the forum, but cannot find an answer to my question.

I have no problems with the heating of my car, or fans not working. But...
Yesterday when I turned the heater fan on full power for the first time, I noticed an extreme noise coming from the fans. The noise gets less when the fan is powered down and disappears when on 1 1/2 leaf or less. It is so loud, that I cannot hear my wife talking when she is sitting next to me on the front row.

Now I have read multiple users describing how they disassemble their fan unit for the controller. I am missing the disassembly steps before that. I had a (actually two!) Haynes manuals for my old C4, but the manual for the C4GP is unavailable. Because of this, I have a hard time figuring out how to take out the fan. Do any of you know how to take it out, or is there a Haynes-like manual that I can buy to figure it our myself?

Thanks for the replies, and kind regards from the Netherlands!


Tom