How to Wire a Union Bicycle Generator

Written by stephan robert
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How to Wire a Union Bicycle Generator
Generator-powered lighting is a good option for low-maintenance bicycling. (bicycle image by apeschi from

Union makes a number of mid-range bicycle generators (dynamos) and lighting systems. The most common are the bottle generators, which are mounted either to the front or rear forks of the bicycle. Power input is obtained from a generator wheel which turns when pressed against a moving bicycle wheel. The wheel rotates a magnet inside the unit which, through the magnetic resistance against a coil, produces an electric current. Dynamo lighting is attractive to those who do not wish to rely on batteries for their bicycle lights. Care must be taken that they are mounted correctly and that they are properly wired.

Skill level:

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Things you need

  • Bicycle
  • Union Generator (or dynamo)
  • Coated wire (provided)
  • Compatible front light (3W or 2.4W)
  • Optional rear light (0.6W)

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  1. 1

    Ensure the generator is securely fitted to the bicycle frame and that the wheel turns when engaged.

  2. 2

    Insert a bare end of the wire into the cable catch at the base of the generator bottle. This is a clip system. Push the tab to reveal the hole, insert the wire, and release the tab. The springs will hold the wire in place.

  3. 3

    Insert the other end of the wire into the left clip hole (a spring clip retains the wire) at the rear of the front light. Some Union models come with the wire pre-fitted. In this case you must simply attach the other end to the generator.

  4. 4

    Trail another cable from the right hand clip hole (or free hole) of the front light. If the generator is powering the front light only, the second cable should be attached to a point on the bicycle frame as an earth. If the generator is powering front and rear lights, the cable must be traced along the bicycle frame to the rear light mount, and inserted into the clip hole at the bottom of the rear light.

  5. 5

    Test the system by spinning the bicycle wheel against which the generator is engaged. Check that the lights go on when the wheel is spinning.

Tips and warnings

  • A brighter 3 watt bulb may be used if the Union Generator is powering only a single front lamp. Otherwise, a 2.4 watt bulb should be used in combination with a 0.6 watt bulb in the rear. Union package systems (generator and both lamps) ship with 2.4 watt and 0.6 watt bulbs pre-fitted.
  • Make sure your wiring follows the frame neatly. Use cable ties to secure it to the frame.
  • Make sure the cable does not snag in any moving part of the bicycle.
  • For front-mounted dynamos, make sure the unit is correctly installed before operating the bicycle. If the unit goes into the front-wheel spokes, you risk a nasty accident.

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