I've very recently bought the Core Racing Charger (Schumacher),

I pu on 1 of my Lipo's to charge and balance it, which so far seems to be taking a very very long time, I noticed there is a fan in the charger at the moment it isnt going. Does anyone know if it kicks in to prevent overheating or if it is meant to be on all the time?

If you're talking about the UDC-20, then that sounds pretty much normal to me. I have one myself, & yes, its balance charge mode does take some time to complete(mine's taken as long as an hour before, when putting a total of 2300mah in the pack, & that's charging at 5 amps in Balance Mode). And yes, the fan should work, but only if the charger starts to get too warm(at least that's how mine's worked)....