RadMini Step-Thru Controller Replacement

Read through the instructions linked above and contact Rad Power Bikes Product Support if you have questions. If you are not confident in your ability to successfully and safely perform all steps, we recommend having the work performed by a local, certified, and reputable bike mechanic.

1. Gather the tools you will need: Flat head screwdriver, flat-side nippers, 4 mm Allen wrench, replacement zip ties, and the replacement controller from Rad Power Bikes.

2. Power off the bike. Ensure the bike is in the off position and use the key to remove the battery. Once removed, press and hold the “MODE” button on the LCD Display Remote until the display remains off for about two seconds (it may flash on briefly). This ensures the power is fully discharged from the bike and it is safe to work on.

3. Snip relevant zip ties. Locate the zip ties in the five locations that will require snipping. These are circled in the image below and accessed from both the left and right side of the bike. On the left side of the bike (left image), zip ties requiring removal include one below the crankset and behind the end of the downtube bundling cables together (center image) and one above the controller, holding it to the downtube (right image). 

 RMST_controller_swap_Zips_L.jpg  IMG_0225.jpg  RMST_Controller_snip_closeup.jpg

On the right side of the bike, the zip tie above the controller can also be accessed. It is circled below for reference. The other three zip ties that need to be cut are all attached to the chainstay (circled below).

IMG_2528.jpg  IMG_2527.jpg  RMST_Controller_swap_motor_cable_snip_close_up.jpg

4. Unplug the motor connector. Once the zip tie for the motor connector has been snipped, grab the side of the motor connector closest to the chainring and pull directly backwards to unplug that connector. The inside of this connector has 3 prongs and 6 contacts along the outside of the connector.


5. Unplug the taillight connector. Near the rear light or zip tied to the optional rear rack (if installed). Pull the ends of the connector apart without twisting. The inside of this connector is light blue with a 4-pin connection.


6. Remove the downtube grommet. At the left side of the bike, locate the cable opening at the back of the end of the downtube and the black, oval-shaped, rubber grommet installed around the edge of the opening. Use a flat head screwdriver to carefully unseat the grommet.  


7. Expose downtube connectors. Use the handlebars to turn the bike wheel to the right, which will provide slack necessary to expose the connectors that are housed inside the bottom of the downtube near the cable opening. Starting at the cable opening at the bottom of the downtube, gently pull out the cable connectors.

IMG_0226.jpg  RMST_wiring_harness_connectors_no_markup.jpg  

mceclip0.png Note: Pull directly on the connector body, not on the cable directly whenever possible.

8. Unplug the three connectors at the downtube end. The three connectors at the downtube end are the wiring harness (1 orange, below), the battery connector cable (2 blue, below), and the pedal assist cable (3 black, below).


9. Thread the battery connector and wiring harness connector through the grommet. Locate the ends of the battery connector and wiring harness connector closest to the back wheel of the bike and back them out of the grommet. Leave the grommet in place, around the (brake and shifter) cables that will not be unplugged.

10. Remove battery tray mounting bolts. Use a 4 mm Allen wrench (or ratchet) to remove the three bolts that hold the battery tray to the seat tube of the frame, located in the middle of the metal strip on the center of the battery tray (see below). Keep the bolts and washers in a safe place for reinstallation.

mceclip2.png  mceclip3.png

Mounting bolts circled                   Battery tray when unbolted

11. Unscrew the old controller. Hold the controller firmly against the seat tube of the frame. Press a Phillips head screwdriver firmly and directly towards the center of one of the four screws clamping the controller to the seat tube. While pressing the screwdriver firmly into the screw, slowly turn each screw about a quarter of an inch to ensure all screws can move freely. Alternate between screws to undo them evenly. 

mceclip0.png Note: Use caution to avoid stripping these screws. Press the controller firmly against the seat tube, press the screwdriver firmly and directly into the center of the screw, torque slowly, and watch for the screwdriver to lift. If the screwdriver lifts at all, stop twisting, recenter the screwdriver in the screw, and twist slowly while pressing firmly.

 mceclip4.png  mceclip5.png

12. Remove the controller mounting hardware. Remove the four screws and two black, metal mounting brackets holding the controller to the seat tube and set them aside until re-installation.


13. Remove the old Controller. Carefully lift the old controller up and to the left away from the bike.

14. Thread new controller cables through chainstay opening. Locate the new controller and orient it so the connectors thread through the opening in the frame behind the bottom bracket (see below).


15. Install the new controller. Carefully thread the two black metal brackets through the mounting points at the front of the seat tube. Hold the controller firmly against the seat tube and install the top two screws. Tighten the screws evenly. Repeat with bottom two screws. Check to ensure equal thread length and that the controller cannot move in any direction.

mceclip7.png  mceclip8.png  mceclip9.png

16. Bolt the battery tray to the seat tube. Locate the three sets of bolts and washers that hold the battery tray to the seat tube and use a 4 mm Allen wrench to re-install this hardware. Test the re-installed battery tray for secure attachment; if the tray can move in any direction, re-center and tighten down the bolts to prevent any movement.


mceclip0.png Note: Tighten down the battery tray mounting bolts until there is no movement in any direction.

17. Thread the connectors through the lower grommet. Ensure the two largest connectors near the downtube end, the battery connector and wiring harness connector, are threaded through the lower grommet and that the grommet is between the connectors and the chainstay. Do not twist the cable and ensure the cables are running straight.

18. Plug in the connectors. Align the two prongs of the black battery connector and carefully press them together to plug in the connector. Repeat with the black 10-pin wiring harness connector, the yellow 3-pin pedal assist sensor. On the right side of the bike, plug in the black motor connector and the blue taillight connector.

mceclip1.png  RMST_Controller_swap_taillight_connector.jpg  RMST_Motor_connector.jpg

19. Push the large connectors into the cable opening at the downtube end. Carefully push the wiring harness and battery connectors back into the opening at the downtube end.


20. Replace the rubber grommet at the cable opening at the downtube end. Grab the oval-shaped rubber grommet and while pinch the long sides together, seat the top of the grommet at the top of the cable opening. Work each side of the grommet onto the sides of the metal cable opening.

mceclip10.png  mceclip11.png

Once only a small amount of the grommet is unseated from the rim of the cable opening, use a flat head screwdriver to very carefully press the grommet back onto the opening so the entire grommet is properly seated.

mceclip12.png  mceclip13.png

mceclip0.png Note: Use extreme caution to press only on the grommet and avoid damage.

21. Install replacement zip ties. At each location where a zip tie was snipped, it should be replaced to secure cables and wires properly. These replacements should be installed on the left side of the bike on properly bundled cables behind the Downtube end and near the Taillight. On the right side of the bike, install zip ties on the cable guide near the chain guard, near the Motor Connector, and along the Chainstay. Use flat-side nippers to snip off excess zip tie.

mceclip14.png  mceclip15.pngmceclip16.png

22. Reinstall the Battery.

23. Test the bike for safe operation. Mount the bike onto a bike maintenance stand, power the bike ON, test all electrical and mechanical components for safe and proper operation, and have the bike inspected for safety by a certified, reputable bike mechanic.

24. Ride Rad!