There are a couple of things I would check. Some units like this have a seperate fuse for heating and fan.They should be located on back or lower portion on sides.Most of these have a black screw on cap. Unscrew cap to access fuse. Always remember to be safe and have heater unplugged before doing any checks or repairs. Most of the older units of this type use old style automotive fuses which are round with a glass center section.You can look at them and see if the wire or metal strip inside is seperated. If it is then fuse is bad and needs replaced with new fuse of same amp rating and size. The other thing is that the heating element is burned out. You can check this by removing front cover or grille and visually inspecting heating coils.Don't mean to sound negative but if it's much more than a fuse you're probably better off to just get a new one. Hope thishelps . Thanks