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Rad Power Bikes Production Site

Radster Road and Radster Trail controller replacement guide

If Rad Power Bikes Product Support determines your Radster Road or Radster Trail has a defective controller, use the following procedure to remove and replace the controller. 

Tools needed:

  • 3 mm Allen wrench
  • Torque wrench with Allen bits
  • Flat side cutters
  • Extra zip ties
  • Bike stand (optional)
  • Nitrile gloves (optional)

Take pictures of cable connections, cable routing and controller placement before you start removing these items, as once you replace the controller you will reinstall everything in its original position.

  1. Get the ebike ready for maintenance. Turn off the ebike, remove the battery, and press and hold the power button to discharge remaining power.
  2. Use a 3 mm Allen wrench to remove the cable and controller cover from the underside of the down tube.
  3. Use flat side cutters to cut the zip tie securing the cables underneath the bottom bracket.
  4. Use the Allen wrench to remove the mounting bolts on the rear of the controller (see Figure 1), and then pull the controller out to access the cables.


Figure 1: Remove controller mounting bolts.


Figure 2: Remove controller.

  1. Unplug the wiring harness cable and battery connector by pulling each side of the connectors apart, without twisting, to unplug (see Figure 2).
  2. Use flat side cutters to snip the zip ties securing the motor cable to the frame and unscrew the connectors and pull apart.
  3. Unplug the PAS and taillight cable connectors.
  4. Remove the old controller and recycle according to local rules (if possible)
  5. Position the new controller with the battery and wiring harness connectors facing the front of the ebike.


  1. Reconnect the battery and wiring harness cables to the new controller by lining up the internal notch and pins and the external arrows of each cable, and press together without twisting.
  2. Reconnect the torque sensor, taillight and motor connectors on the other end of the new controller.
  3. Mount the new controller in the frame in its original position.
  4. Use the Allen wrench to re-install the controller mounting bolts. Use a torque wrench to tighten the mounting bolts to 2-3 Nm.
  5. Use new zip ties to secure the cable runs you cut earlier, and use flat side cutters to snip off any excess from the zip ties to ensure the ends are flush and smooth with no sharp points.
  6. Reinstall the controller cover and frame cable cover and tighten the mounting bolts until secure.
  7. Reinstall the battery, test the bike fully, and ride Rad!
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