Replacing Aurora Limited Harmony Power Cable

John O'Donnell

Modified on: Fri, 3 Nov, 2023 at 7:45 PM

Replacing the Harmony power cable is relatively straightforward. The instructions below detail the process. Note that the photos are taken with the bike right side up, but this procedure is most easily done with the bike inverted. You will want to rotate the display out of the way so that it's not damaged, and lay down a towel on which you can rest the handlebar and saddle. The bars will provide enough stability to work on the bike.

You're going to have to lift the motor up (with the bike inverted) to access the cables. The biggest trick in this whole process is routing the cables so that everything fits back into place--so you'll want to note the wiring as you're lifting up the motor. This will also be detailed at the end of this e-mail.

Power off the bicycle and remove the battery.

Using T10 Torx driver, remove two bolts that hold the motor cover on

Loosen rearmost motor mounting bolts with 5mm allen wrench - the bolts enter from either side and thread into the motor casing. DO NOT LOSE THE LOCKING WASHERS ON THOSE BOLTS- sometimes they stick to the paint

Before you remove the motor, you will want to remember how the wires are routed around the motor mounting points. It is best to take a picture so you can route it the same way upon installation. There are 5 wires that are routed from the frame and make a connection to the motor unit (list/diagram at the bottom).

Now you can access all motor mounting bolts - remove the remaining 4 with a 5mm allen wrench. Leave the rearmost bolts in place loosely to support the motor. DO NOT LOSE THE LOCKING WASHERS ON THE MOTOR BOLTS- sometimes they stick to the paint.

After removing the forward motor bolts, tilt the motor to gain access to the wiring.

You can now see the large blue Harmony plug. This is the likely culprit with the failed solder joint, and the cable which you'll be replacing. After you route the cable through and connect it, I would suggest powering up the bike to confirm that you have power to the shifter, just to make sure--then you can reinstall the motor.

Installation is reverse of removal.

Make sure to route wires/harnesses the same as they were before. The wires often have a memory of which way they were curved, so following those will make installation as easy as possible. Be careful not to pinch or crush any wires/plugs when the motor is installed. There is no force needed to push it in place if the wires are routed correctly. If force is required, a crushed wire or plug will result. Be patient. Inverting the bicycle might make this easier as gravity will help keep the wires in the proper spots as the motor is laid in place.

The easiest way to route the Harmony wires is as shown below. The yellow wire is from the shifter and passes over the mounting bolts and up into the battery dock void. The red line is from the rear axle, through the grommet, over the mounting bolts and into the battery dock void. There is enough space in there to place the blue and black connectors.

NOTE: The blue and black connectors for harmony are under the battery dock. There is still a juliet-style push/pull connector and bullet connectors for the Harmony power under the motor cover.

The rest of the wires are not as hard to nestle in the voids after the motor is bolted into place. Its possible tuck the rest into the open spaces between the motor mount and motor as well as under the motor cover.

The easiest way to route everything is as follows:

Harmony harnesses-as shown in picture above.

Main harness-as shown by the red line in picture below. Route it over the first motor bolt and then down instead of down in front of it

The light and speedometer wires can easily pass in the gap marked by the yellow line A in the picture below. You have to fit the wires in the gap before bolting the motor on. Tuck the excess in void marked B.

You can also route wires going to the back over the controller, tuck the excess in the void marked B. The cover fits on still.

All other wires and slack can be tucked into the area marked C.

Only the hydraulic brake and the Harmony harness passing between the motor and the mounting plate.

One the motor is secure, you will reinstall the cover, chainring sprocket and crank arms. Check chainring bolt tightness before installing spider/chainring as access is currently very easy on both sides. When installing the lockring (turning to the left to tighten), make sure it is very tight to prevent creaking.

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