Before you start anything, it's worth having a quick look at the pedal sensor behind the chainwheel. There should be a gap of about one millimetre between the disc and the sensor, and it it should stay like that while you rotate the crank. Sometimes, the magnet disc comes loose on its shaft and doesn't turn with the pedals, so put some slight pressure on it with your finger while you turn the pedals to test that it's fairly tight.
Other easy to check things are the motor connector, which is about a foot from the axle on the right side. Make sure that it's pushed in all the way to the line, and check that the motor cable isn't damaged where it comes out of the motor.
The LED control panel has very little affect on function. It's a good indicator of battery condition. If it goes off by itself when pedalling, it means you have a problem with the battery, but if it stays on, your battery is probably OK.
It works like this. It has a battery voltage supply direct from the battery (red and black wires), so it works independently from anything else. When you switch it on, it activates a wire that returns battery voltage to the motor controller to power it (blue wire). That's it's first function to work as a power switch for the motor controller.
Its second function is that it has a wire that provides a signal to the motor controller (green wire)to tell it which of the three speed levels to maintain when you're pedalling. The wire has 1v for level 1, 2v for level 2 and 3v for level 3. If there's no voltage on it, the controller defaults to level 1.
The third function is to display the battery charge condition. It displays the number of LEDs along the top according to the battery voltage.
Fourth function is to switch the lights, which it does by the 5th wire (probably yellow).
To test your bike, first switch on and check that the LEDs show that you have enough voltage. Next, pull your motor controller out of the compartment in the rear part of the frame (remove cover first, which you access when the frame is folded). You then need to identify the pedal sensor connector, which will have three wires either side, probably red, black and another colour. Measure the voltage between the red and the black by sticking your probes up the back of the connector. Remove any hot-melt glue that prevents that. You should see around 5V. that tells you that the controller is switched on and active.
If you have the 5V there, measure the voltage between the black wire and the not-red one, while you turn the pedals slowly. You should see 5V switch on and off as each magnet in the disc passes the sensor, which will be something like five times per rotation. It only has to switch once to confirm that it's operating correctly.
Come back when you've done those tests.
Motor controllers are generally pretty reliable. I'll be surprised if you need a new one.
