Smart Pie 4 Acting Up

[Brendon1128]

Hey everyone,

Tonight I charged up my battery in prep for my cycle ride home from work. When I went to plug the battery in, the battery charge lights lite up to green and looked good. By accident, I hit the red reverse button on my throttle. I've done this before a few times while cycling, and what ends up happening is the lights all go out. If I hit the button again, they come back on. Well this time, I started to smell burning plastic. I immediately unplugged the battery and let everything cool off. I checked all the connections to make sure nothing was damaged.

Everything looked ok so I plugged it back in. Now, the lights don't come on at all. The red empty light flickers on and off. When I twist the throttle, it delivers full power so its working at least, but the battery level gauge isn't working. I still have to cycle home so I'm hoping my ride with be fine.

Any ideas what this could be? Do I have a faulty throttle or something? I don't have or use the reverse button, but why would it cause the gauge lights to fry? On my old SP3 motor, the reverse button didn't do anything to the system. With the new SP4, is it linked to something else like the power?

[GM Canada]

What button are you considering is the reverse button? Any Smart Pie v1-4 that passed through my hands has no reverse funtion unless you do an extra hookup like this.

https://m.youtube.com/watch?v=BPxOKDIz0_A

If you did not attempt this maybe the some of the unused wires are touching or gounding out somehow?

Gary

[Bikemad]

The main harness doesn't usually come with connectors fitted for the horn or lighting, and if the insulation on the wires has shrunk back a bit, it is possible that the copper wires could be touching inside the heatshrink tubing used to cover the exposed wires, causing a short circuit similar to the one Wesley had with the unfinished wire on his motor harness:

I don't know what its for bc I have not been able to find a wiring diagram but I think it's for lights, etc. Anyway these wires were cut clean from the factory and it seems after some use the insulation was pulled back and these wires made contact with each other.

The four wires will be the same as the ones shown for the MPIII as they are for pedelec and reverse function:



If the pedelec red +5V wire shorts against the black ground wire it would effectively disable the throttle as it also shares the same 5V supply. If there was no 5V supply at the throttle hall sensor, then no throttle signal voltage would be produced when the throttle is operated, and therefore the motor would not run.

I don't understand why the wires are simply left incomplete like this and I would prefer to see them pre-fitted with a sealed connector socket and supplied with a matching plug on the end of a short length of cable which could then be wired as required by the customer if the additional functions (pedelec or reverse) are needed.

This also applies to the horn and light connection on the main control harness too, because on this type of product I think it's essential that all of the wiring should be plug'n'play compatible to allow quicker and easier installation.

If six months after fitting the motor kit you decide to purchase a GM LED front light with a built in horn, you should be able to simply bolt it into the correct position and then plug it directly into the harness so that it would be instantly ready to use.

Brendon, as your throttle is still working, the short will probably have burnt out the thin battery feed wire going to the lighting switch in the throttle which is used to supply the battery gauge LEDs and also the square Red switch which is wired to supply front and rear LED lights if fitted.

If you're lucky, the wire will have fused inside the throttle unit istelf, and a replacement throttle will cure the battery gauge fault. But if you're unlucky, the wire will have been damaged somewhere inside either the main front harness, or the controller harness, which would not be quite so easy to rectify.

The problem is most likely to have been caused by the Red lighting feed wire touching against one of the Black/Blue ground wires on the unused cable coming from the six way junction on the front harness.
A similar fault can also occur if the horn button is pressed while the Yellow horn supply wire is touching either of the ground wires.

Alan
 

[Brendon1128]

Hi Alan and Gary,

I don't have anything plugged in except the throttle and e-brakes. I don't use any of the other plug points, and have sealed them all with electrical tape to prevent water damage (since I cycle in the rain too) I don't use the horn, reverse, or GM headlight since I have my own rechargeable one.

The button that I was talking about was the red button on the throttle which I'm not sure what is for. I thought it might have been a reverse button for people who use reverse. So far, I've ridden the bike about 200 miles since this happened, and everything works fine. It's just the battery gauge lights don't illuminate anymore. I can't imagine what could have happened; should I request a new throttle?

[Bikemad]

Hi Brendon,

If you have a thumb throttle it is relatively easy to access the wiring inside to see if the red wire has broken inside the throttle housing. If you have a twist throttle it is not very easy to access the internal wiring without damaging the plastic cover.

A new throttle may indeed rectify the battery gauge fault, but if you press the red button again it will probably burn out the new switch wiring and/or the main/motor harness wiring.

The reason for the short needs to be located and rectified to prevent further problems, and I suspect the root cause of the short will be found inside the electrical tape on the end of the unused short cable on the main harness as I previously described:

The problem is most likely to have been caused by the Red lighting feed wire touching against one of the Black/Blue ground wires on the unused cable coming from the six way junction on the front harness.

Alan
 

[Zerogee]

I had read the warning just before hooking up my SP4 to examine those open wires to see if their jackets had shrunk resulting in exposed filaments and shorted wires. Sure enough it looked like the jackets had shrunk and filements were in contact with neighboring wires. So I cut to outer black jacket back 1/4", cut the tips of each wire clean. I didn't have heat shrink tubing that small so I folded each wire back over the black jacket into their own quadrant (seperating each wire), then covering them with heat shrink.

If you have not done anything like this to properly terminate these ends its worth a look at it now. Chances are the jackets on those wires have shrunk by now exposing the wire ends and they are touching.

I guess GM assumes those wires will get used right away by every consumer so they don't bother to terminate them properly. 
Dumb!

[Marsbar]

Yes, found the wiring diagram. The green button is for horn, the red for Cruise control!

And, the on/off button is for lights.

Will try to wire up.

Looks good, but don't think the buttons will last long in the rain. Will wire up the cruise control button now and test it!

For the plugs, I have inserted White Vaseline to avoid corrosion and water ingress...

The plug system seems smart, but better in the old days because you could do fault finding more easy in a junction box... f one plug fails you have to replace the whole cable system...