Replacing a crank sensor

[Toonces2]

I've had this Schwinn Mendocino ebike for about a year now, and the only time it worked properly was when I test-drove it and bought it slightly used. It's a pedal-assist bike, and when I got it home, the assist would only kick in part of the time when I was pedaling. As the guy I bought it from was an ebike mechanic, he said it was probably the crank rotation sensor and shipped me a replacement. The only problem is the wire on the one he sent me is too short, so now I'm striking out on my own to figure this thing out.

The first picture shows the bike's original crank sensor circled in yellow, as well as the wire end I cut from it. Hoping I didn't make a mistake in cutting that wire. The circular sensor seems to be pressed into the frame somehow, as it shows no signs of coming off. The mechanic guy said don't worry about that; leave it on and put the other crank sensor on top of it, and it should work fine. The top of the picture shows where I traced the sensor cord back and unplugged it right before it goes into the battery case. The end is circular and has three small pins.

How should I go about fixing this bike? What sensor should I order?

Also, I took it apart about a year ago and don't remember exactly how the wheel with magnets in the second picture integrates into the whole mechanism. I'm sure it didn't come with the sensor he sent and that it's part of the original crank sensor system. Would it be ok to leave this magnet wheel off when the new sensor gets put on?

 

[gromike]

Buy a new PAS crank sensor unit with the same magnet count and a Julet plug. Install their magnet wheel and place the sensor per the installation instructions.
Though, you might need to enter the set-up mode and your display can't do that.

 

[harryS]

The sensor bracket is a ring that is held onto the bike by the fastener on the bottom bracket (BB), Here's a pic of a SHimano nottom bracket removed from a bike. You can buy a tool to remove the fastener which is shown separated from the BB. I own one of these tools and it can get complicated. I believe the fastener is right hand thread, and one often has to use some tricks if the fastener is too tight.

Usually, when a pedal sensor works intermittently, it's not electrical. Your magnet disk is either too far from the sensor, or it is slipping on the pedal axle. I've fallen victim to both. When these disks get like 5 years old, the plastic seems to turn into stale bread. ,

It's too bad you "removed" the wire or you could try adjusting the disk. The magnets on the disk should be less than 1/8" away from the sensor.


If your old sensor is trashed or you know it doesn't work. you can buy an all-in-one integrated senor which just slips onto the pedal axle. Then there is no need to buy a tool and remove the old one. It also eliminates a lot of installation issues.

The pic shows both syles, The one on the right is the all-in-one and it has a round three pin connector that hopefully matches the one on your bike.