I have a Citroen Picasso Xsara 2001 and the heating/fan system doesn't work at all.

We changed the main fan, the one that looks like http://www.bradgatemotors.co.uk/spares/media/gbu0/prodsm/u_picasso_hmotor_fj40630.jpg.jpg that but it made not a single bit of difference. What else causes complete failure of heat/fan systems?
I've thought of fuses but would need to know where they are.

Any help is awesome.