peugeot expert windscreen steaming up

hi can some one help me i've got a peugeot expert and the windscreen keeps
steaming up but it seems when you but the blowers on to screen hardly any
air is coming out any ideas

 

I had this problem with a 405 once and it turned out to be very small leak
in the heater core. This eventually made the carpet damp also an odd sweet
smell which I was told came from the antifreeze.

 

Does that model have a cabin air filter? If so it is probably choked up with
debris.

 

I had this problem with a couple of 405s and changed the matrix ... but