Incorrectly installed fuses, incorrect fuse types, intermittent shorts and overloaded vehicular circuits can all cause frequent electrical malfunctions. If installed fuses are designed to carry less wattage than the radio requires, they will blow. Similarly, if too many electronic components are wired onto a vehicle circuit, their combined operation will cause the fuse to blow.
The cause of a blown fuse depends heavily on the electrical content of an individual vehicle. Car circuitry is dependent upon model and also upon previous repairs or electronic additions. Before beginning the repair job, it is important to ascertain which other electrical components, if any, are wired into the radio's circuit. The combined required wattage of all electrical devices on the circuit have to be taken into account when figuring the correct fuse type.
If the correct fuse rating is installed but the circuit continues to cause the fuse to blow, an intermittent short could be to blame. Old or faulty wires with partially-missing cladding are often the culprits of a short. When two bald wires touch, a circuit may become overloaded, causing its fuse to blow.
Technicians can locate a short using an ohmmeter, a voltmeter or a multimeter. When the short it identified and fixed, the correct fuse type for the circuit will no longer blow.