This information is for three position e-units with a single winding on the field.
If the motor runs in one direction but not the other. . . sequence is forward -neutral - SHORT or NOTHING - neutral - forward, then a wire to a brush and the field wire are reversed. I did this last weekend.
The E-unit has three wires coming off the lower contacts. There is also a wire from the center rail pickup to the lug beside the lever.
- If two are the same color and the third wire is a different color, the odd color usually goes to the field.
- If there are three different colors and one is green, green is the field. This is shown in one of the photos below.
This Postwar F3 e-unit has the green wire on the upper left. Green to field, yellow and black wires to brushes.
Here's a diagram of the wiring of an e-unit:
Wire colors to brushes are not the same for all e-units.
If the motor runs once and then not at all, the drum might be in upside down. That sucks, but it's how we get good at changing them.
Another reason the motor may run once, then not at all is loose connections of the wires. Make sure you check the field connection. You check field by connecting a wire to the ground, and then the other lead into the green wire above. Should buzz and short.
Check for bent fingers on the e-unit. Sometimes a finger will break off. This happens from bending the fingers while replacing the drum, or can happen because the drum is defective.
