But it is worth it,
In order to draw current you need a complete circuit. In the case of an automotive electrical system, that would entail a connection from the positive 12-volt battery terminal (supply) to the negative terminal (ground or chassis). The blower resistor is in series (on the supply side) with the blower motor. The blower motor completes the path to ground. The blower resistor creates a â??voltage dropâ? between the motor and the 12 volt supply that causes the blower to run at a lower speed (Ohms Law, E voltage drop = I current x R ohms. By Ohms law the voltage drop creates heat at the resistor (P watts=E volts x I current). The motor will draw a set amount of current based on the applied voltage (12volt supply - series resistor voltage drop). Increasing the resistance will slow the motor and pull less current, decreasing the series resistance will speed the motor and pull more current. Even with a shorted resistor, the max current through the fuse would not reach 30 Amps. It would be the same as when the fan switch is set to high (resistor shunted â??shortedâ? out of the circuit).
Since there is no â??groundâ? connection on the blower resistor it cannot supply a return path for the current and cannot cause the fuse to blow. All it would do is force the blower to run at full speed all the time. Not to mention that in my more then 35 years of electronics I have never ever had a resistor fail â??shortedâ?, even wire rounds.
What will blow a fuse is,
A bad blower motor.
Exposed wiring due to insulation damage.
High resistance on the fuse terminals causing excessive heat at the fuse.
The reason this is important is that the source of the short must be found and repaired.
I donâ??t want to read the next post saying, â??I had to jump out of the car because it filled with smokeâ?.
jeff
