Heater Blower Problem on Laguna

Hi, This is my first post so hello! I have a 1997 Laguna 1.8i RT Sport which I love apart from the fact the heater blower motor (for inside the cabin) has started to stop working now and again. When it works its fine on every speed (1 to 4), but when it stops working it might stop for a few days or mabey just for a few minutes. I replaced the heater blower motor but that hasn't solved it so I presume its an electrical problem but I don't know where to start looking. Any help is much appreciated. Keith.