I have a nissan serena 'L' and the front heater blowers keep fusing so while I have heating it does not blow it around the vehicle. I have replaced the fuse repeatedly but it keeps blowing within 5 mins.
Sounds like your blower motor is pulling too many amps and blowing fuse ...make sure you have right size fuse and then disconnect blower motor and try all speeds to see if you can get it to blow fuse ....if it doesn`t blow fuse I would say blower is faulty and needs to be replaced