The heater is a small radiator. If running the heater brings the temperature down, most likely the radiator fan is not turning on. If there is a blown fuse, and replacing it solved the problem for two days, it is fairly certain the fan motor has tight bearings, and that is making it draw excessive current, which will blow the fuse again.
Wires rubbed though can cause a fuse to blow too, but a tight motor is more common. If you can reach the fan blade and give it a spin, it should spin freely for many revolutions. If it has tight bearings, it will stop spinning as soon as you let go of it.
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Monday, May 1st, 2017 AT 7:02 PM