issues with air boxes and hot/cold air

[hpmad]

hello,

I am trying to fix a couple of issues in the 'climate control' of my 80 SC...

I need to remove the blastic air 'exchange' box tucked behind the brake master cylinder under the bonnet (hood for you americans)... how in hell do I do that? it's unaccessible? do I need to remove the master cylinder? can I do that without having to remove all the break fluid and then blead the breaks?

also, I am trying to unserstand why the fan does not come on when I move the cold air selection switch toward the right. can anyone point out what are the main items to check there?

I wan not able to find any information on these items either online or in my various books...

thanks, cyrille