PaoPao

Dear all, I've just bought an Orange Terror Bass 500 amp (newer version mk2). It works well and sounds good. But the fan is not runnig at all (i can see it motionless from the grid). Is it like this? Does it start just when it is necessary (high temperatures) or there is something wrong with it and need to be repaired? I don't want to overheat it and avoid problems and damages. Thank you for your help