Background

My post-op chemotherapy treatment for my adrenal cancer meant I was struggling to get any fitness, so in 2019 I bought a Ribble CGR-ALe ebike based around the Mahle X35 system. It was in fact pre-ordered prior to the bike’s initial release by Ribble.

This bike served me well, getting me out and about before any fitness returned. Since getting fit again, it has also proved useful for my 20KM each-way commute. Allowing me to avoid the traffic jams but still get to work without getting too hot and sweaty.

The Problem

A few months ago the bike developed a problem, the power assist just cut out. As it is well outside any warrantee period from Ribble, I took it to my local bike shop, who are a Mahle certified service centre.

They initially thought it was probably a failed PAS Sensor (the pedal assist sensor), but then discovered that cleaning the existing PAS connector (to the battery) and ‘jiggling the cables’ they could fix the problem. This suggested the problem was the cables/connectors and not the sensor itself. They recommended the only ‘official fix’ was a battery replacement, which includes the wiring harness, at a cost of well over £500.

This was an amount I was not willing to pay as:

1. It was working again (at least at that time)
2. I thought I could fix the problem by re-wiring the PAS sensor to battery connection myself (such rewiring was not a service the bike shop offered)

I used the bike for a few moth, but last week the bike started to intermittently deliver power. On each pedal revolution the power surged on and then off. This obviously pointed again to a PAS sensor issue, so it was time to reconsider my options.

The Solution

As I was still not willing to pay £500+ to fix a dodgy connection, I realised it was time to look to my soldering skills.

The first step was to get access to the connectors. I had lost the plastic cover over the cable access point under the bottom bracket soon after the bike shop had looked at the problem, so it was easy to get at the eBike cables.

The issue was that due to corrosion they had had to drill the tiny screws out that held on the plastic cover so they to get access to the cables, so it was never really held securely after that time.

This lack of a bottom cover, and the winter road salt, were no doubt part of the whole problem. The bike as you can see in the photos is showing it’s age. I would be lying to say it has been washed down and dried each time it is used.

Trying a new PAS Sensor

My previous visit to the local bike shop had left me with a spare PAS sensor. So I temporarily connected this, routing it outside the frame. When I tested this setup I got an interesting effect. The pedal sensor worked, starting the motor when I turned the pedals, but it did not stop when I stopped pedalling. In fact the only way to stop it was via the main power switch.

Very dangerous to ride, so that was not the solution.

Cutting the cables

The change in behavior between the two PAS sensors told me two things:

1. There was nothing wrong with the motor or battery
2. The problem really must lie in the electrical connection between the battery and the PAS Sensor, as I had always suspected.

So, it was time to cut the cables and remove the connectors. Connectors that looked internally fragile with very fine pin, a number of which looked green with corrosion

Once removed, I used a multi-meter to confirm that Mahle had been consistent in their choice of wire colours. They had, using the orange, brown and black wires, the only three wires in a PAS cable assembly. From the battery side there are two more wires, green and white, but these were not used.

I then soldered the original the PAS sensor to the battery unit, turned the pedals but nothing worked.

Replacing the PAS Sensor (again)

So time for more cable cutting, this time I cut the end off my new PAS Sensor and again temporarily fitted it.

This time when I pedalled it worked. So it seems the issue was both a failing PAS sensor and a bad connection.

Tidying Up

My final problem was to neatly fit the new PAS sensor. Like most bikes with any internal cable routing, everything is awkward.

However, I was able to use the old failed PAS sensor as a pull-through. This only worked because I had cut the connectors off both the old and new cables. I was able to join them with some heat-shrink, which was thin enough to wriggle past the bottom bracket, the space would have been too small to get a connector past otherwise without removing the bottom bracket.

Once this was done I was able to solder a more permanent connection for the three wires and use layers of heat-shrink to protect the joints.

Summary

I have now used the bike for a commute, and it does seem smoother to ride. This could all be in my head, but it is also possible that the PAS sensors and connections have been failing slowly. Being intermittent for a while, causing a less smooth power delivery, that just became very noticeable last week.

The key point though is that I again have a working eBike, it just required me to be brave enough to cut the cables and remove the failed parts.

I hope the steps and photos may help someone with a similar problem.

For the original version of this post see Richard Fennell's personal blog at Fixing Ribble CGR-Ale (Mahle X35 based) ebike with intermittent power