Have no heat can it be a fuse?

Heat comes from the heater core, which is always on, it's like a mini-radiator, with two coolant lines coming from the engine. A temperature blend door will direct air from the blower motor over it to provide heat, or the blend door will close and bypass the heater core. If you have no heat, then there is a problem with the heater core. (from this point I'm assuming you have a working blower motor.) The first thing to check is the engine coolant levels. If that's good, then check the two coolant hoses that run to the heater core, they're about 1" in diameter. They should feel pressurized and hot. If not, then you may have a constriction or blockage in the heater core, you might be able to flush it out (like any radiator they can accumulate rust and gunk).