Reply to "How to Make A Williams Engine Run Slower"

For your horn issue, put diodes in series with each motor, that will allow the horn to get the power it needs, but lower the voltage to the motors several volts to give you the slow speed operation. You'll need diodes facing each way in parallel, each set of diodes will drop the voltage around 0.6-0.7 volts. I'd use 6A diodes, I'm pretty sure one motor won't tax those. You could probably use 3A diodes with no problem. Using 4 diodes in each direction, you'll drop the voltage around 2.5 volts to the motors.