Should I replace my controller?

[Manassasralph]

I bought a used bike with a MP motor.  A previous owner had some other device connected, which had wires simply cut.  Some of these wires were spliced with the MP controller wires.

The motor ran most of the time, but occasionally it wouldn't run and I could hear, what I think was a short circuit pop.

I decided to eliminate the extra wires.  The controller wires (close to the motor) have been spliced into, and some wires are cut (not connected to anything).  Now, when power is applied to the motor battery leads, I get a short circuit arc.

Bottom line, should I replace the controller, so the controller wires will be good?  Can the controller wires be replaced by Golden Motors?  What is the likelihood, the controller has been fried due to the splicing?

Suggestions welcomed

[Bikemad]

Now, when power is applied to the motor battery leads, I get a short circuit arc.

A momentary spark when the battery is first connected is quite normal, but if the spark is big enough to melt the ends of the wires then there is definitely a problem somewhere. Try connecting through a 5 or 10 amp fuse and see if the fuse blows. If it doesn't blow, then you probably don't have a short circuit in the controller.

The typical spark experienced when connecting the battery is due to a sudden high inrush current flowing from the battery to the controller as it instantly charges up the controller's capacitors from 0V to full battery voltage in a fraction of a second. 

Which Magic Pie do you have? I presume your motor has an internal controller?

Bottom line, should I replace the controller, so the controller wires will be good?  Can the controller wires be replaced by Golden Motors?  What is the likelihood, the controller has been fried due to the splicing?

If the controller is dead, you will obviously have to replace the controller, but you would then have to cut the wires to splice it into the existing wiring, or fit a new control harness, brake levers, throttle and cruise button assembly.
It's impossible to say whether the controller has been fried due to the splicing without carefully inspecting and tracing all of the wiring.

I haven't seen the controller wiring harness being sold separately and I don't think GM offer a service where they would replace just the cable on your controller, but if it's available separately and it was replaced, you would still need to use a new control harness, brake levers, throttle and cruise button assembly if you want to avoid cutting the new controller harness.

If the wires have been spliced correctly to the correct wires on the bike (and they are properly insulated) it should not cause a problem, but if they have been spliced incorrectly to the wrong wires on the bike (or the connections are poorly insulated from each other) then it could possibly have caused damage to the controller and possibly the Hall sensors in the motor and/or the throttle unit as well.

As the bike has been running "most of the time", I suspect that the wires must have been spliced into the correct wires at some stage, but as we have no pictures of the affected wiring, or informative details of your bike, and don't even know which Magic Pie has been fitted or how it has been wired into the bike's existing wiring, it is difficult to offer specific advice.

Is there any indication on the bike when the battery power is on, and if so, does it remain on when the motor stops, or does battery power disappear when the motor stops?

Could it be a poor battery connection or a power switch problem?

Alan
 

[Manassasralph]

Alan,  Here are some photos.  You can see the power wires are cross over (red/black + black/red).  I thought this was part of the issue, so I connected the battery red to the controller red/ battery black to the controller black.  This caused an immediate short.

Did I fry the controller?  What should be my next step.  Take off the wheel/motor, remove the controller, examine?

What about the thin controller wires?  Again, sketchy connections.  Can they be tested?

When I now connect the battery (crossing the black to the red), I get nothing on my thumb switch LEDs.

[Bikemad]

The top photo with the two red HXT 4mm Bullet connectors shows what appears to be a shunt unit for a Cycle Analyst.
You do not need to use any of this wiring assembly as you do not have the Cycle Analyst display unit to go with it. 

Unfortunately, it is quite possible that you will have damaged the controller by supplying it with reverse polarity battery voltage. 
Let's hope that it has not damaged the Hall Sensors in the motor at the same time.

If the battery gauge LEDs on the throttle no longer light up (assuming they did before) then the throttle unit will also have been damaged by the reverse polarity. 

The wiring in the second picture is a bit of a mess to say the least, and I have no idea what the connections would be on the top cable with regards to the connections to the controls at the other end of it.

It appears to have three thick wires (Yellow, Green and Blue) which presumably connected to the phase wires on the original motor, and six thin wires (Red, Black, Yellow, Green, Blue and White) five of these would have connected to the Hall Sensors and the White wire was probably used for a temperature sensor (or possibly a torque sensor) incorporated into the original hub.

These wires will have been repurposed by whoever changed the motor, so it is impossible to say what purpose each wire has been reassigned to without tracing every wire individually to see where they all go.

The other end of this cable would have gone directly to the external controller that was originally fitted elsewhere on the bike, and the controls (throttle and brakes etc.) would also have gone to the external controller.

As I still have absolutely no clue as to what bike you actually have, I'm guessing that the original controller might have been mounted in a separate compartment near the bottom bracket. 

If it were mine, I would simply remove all of the existing original wiring and replace it with the correct harness and controls (brakes, throttle and cruise/horn button assembly) to match the new controller, which I suspect you are now going to need. 

Alan