Help! Display lights don't come on any more on an URBANMOVER.

[Benton]

I have used two URBANMOVER ebikes since 2008. They are the folding UM24 and the UM55 Cruiser. The UM24 was stolen
in 2016; so I bought a virtually new UM55 in the same year with the insurance payout, which has a thumb throttle. They
have changed my life in the last 16 years! Praises for both models can be given in a future posting, if anyone is interested.

When the battery is switched on the lights on the Throttle will come on, but the lights on the very simple Display Unit
that came with the UM55 (Photo 1) will only light up after the Power button on the Display Unit is pressed. Now none of the
lights on the Display comes on when the Power button on it is pressed. Photos 2 and 3 show both sides of the Printed
Circuit Board inside the Display Unit. A volt meter shows that the voltage between the Red & blue, Red & Green and Red &
Yellow is all 24V. Oh, the brushless motor is no longer turning.

I was told that a resister or capacitor on the Display pcb might have been blown, or become disconnected due to any poor
original soldering. If you could help me find that culprit, I should be ever so grateful. By the way, I have checked that all the
connections in the Control Unit are in perfect order. The Control Unit is not to blame either, since replacing it with a new
Control Unit made no difference.

 

[Nealh]

The black GND /Ground wire is broken, it needs to be resoldered to the black end coming out of the main trunk cable. In #3 you can see the broken end , you may have to strip the black outer sheath back to expose a bit more of the Gnd to solder to or if the trunk supply cable is long enough cut it back 10cm and resolder all connections to the PCB . Don't forget to slide a piece of shrink insulator down the wire before doing the joint.
If doing the latter don't just cut the wires as one group otherwise you will short the controller and do damage, cut one wire at a time and solder it to the PCB before the next one .

 

[Nealh]

Looking at #2 the solder on the diode ? top right looks a bit holey and a bit iffy .
Also the resistor middle of PCB very RHS has a iffy holey solder.
But first make the GND connection first as without it you have no chance.

 

[saneagle]

If you can't fix the display, you can work your bike without it. Its main function is as a switch. It switches power to the controller. When the controller is powered, your throttle will work and you get fixed lowest level pedal assist. All you need to do is bridge the red wire to the blue one on the control panel's connector. That's what's done by the control panel when you switch it on and off. There's nothing stopping you from putting a normal switch on that bridge if you want a more convenient permanent solution.

As Neal points out, your ground wire has been cut. It can't work like that, so that's probably the root of your problem and it needs fixing first before considering the above.

The white cable tie is supposed to be around the black outer sheath. It's there to perform the vital function of stopping the cable from getting pulled out. It's position now shows that the cable has been pulled so hard that it been dislodged. When you reassemble, you need to fit a new one.

 

[Nealh]

The red to blue is a good quick fix to get you going but then one is limited with the PAS option, not to critical with the speed controllers but with a current control systems one loses the much greater versitality of such a better system.

 

[Benton]

Thank you so much, Nealh, for pointing out the broken Black earth wire. I hope lo mend that in the weekend. Thanks also to saneagle for explaining the purpose of the buttons on the display panel.

 

[Nealh]

Do let us know how it goes, we should here good news once the Gnd is reconnected.