Then again..
The motor does pull around 50 Watts at full voltage, which is not 12 volts, it's 13.8 volts. As you put the Voltage Dropping Resistors in series with the motor you get the confusing part.
The Current that is drawn changes as each of the added resistors cause the voltage to decrease.
In low speed you have a total series resistance of 5.7 ohms. I=E/R so you will have I=13.8/5.7 which = 2.4 amps. P=E, 13.8 x2.4 = 32.64 Watts.
The Power that is lost to the motor is due to the resistors and their voltage drops. Remember as you change series resistance the motor current changes!!
To figure the "voltage drop" across each resistor I had to figure total series resistance for the low and medium settings. LOW has a total series resistance of 3.7 ohms (motor), and 1.0 for the LOW speed resistor and another 1.0 ohms for the MEDIUM resistor. This all figures out to about 2.4 amps drawn in LOW speed, 2.8 amps drawn in MEDIUM, and 3.8 amps drawn in HIGH speed. Series circuit amperage is the same through all the series components.
Use E=I/R, and you'll see the various voltage drops as the resistors are added and removed. POWER dissipated by each resistor must be calculated individually as they are added or removed because the amperage changes and thus, the voltage also changes going thru the resistor!
So, making a long story short: In low setting 5.6 Watts will be dissipated in "both" the 1 Ohm resistors, and in high setting (Remember you have only one resistor in series now.) The medium resistor will dissipate 7.8 Watts. The best way to handle this is to get two 1 ohm, 10 watt power resistors. Axial, Cement Wire Wound. Mouser Electronics and sometimes Ebay are good choices for finding them.
The one that has three leads that comes on the original switch has a 5 watt power rating. THAT is why they burn up when applying 12 volts to them. This is not over because now I have to figure out a way to hide these two (larger) 10 watt resistors. Rather than wasting my time on an AD Toaster, I think I will concentrate on a good place to hide the resistors. Any ideas?
