I’m confounded by what seems to be a simple modification to my Atlas built Alco S-1/S-3. I want to add a headlight to the rear of the switcher. It’s fine with me that both lights will operate simultaneously. I’ve tried soldering a grain of sand bulb (with a resistor that protects the voltage of the 1.5V bulb) to the leads on one end of the terminal strip. The same side as the front head light. The bulb does not illuminate. If I disconnect the terminal strip screw and thus disengage the motor, both bulbs illuminate. Can anyone help this electrically challenged model railroder? Thanks if you have any advice.
First; you may melt the plastic using a 12/14 V bulb, and a resistor which drops that amount of current from 12V to 1.5V will get hot. In addition, there will not be enough voltage for the light to light.
But you have other problems. I believe that you have connected both wires to one side of the motor. When you disconnect the motor, the current has to flow through your added bulb to flow through the orginal bulb. When you connect the motor, the connection completes a circuit which shorts out the leads to your bulb. I do not understand how your resistor is in the circuit.