Thanks for coming back to me Nealh. It all began when I was riding along, and suddenly I hear this awful grinding noise. It did sound like a mechanical problem. When I got home I put the bike on the stand and turned the cranks. It would then either not work all or sometimes start up with the grinding noise again. Holding the minus button for walk assist results in no movement at all. The lights on the display on top of the battery pack come on as normal. I've done a factory reset, but still nothing. The light on the PAS flashes as I turn the cranks.
Thanks again for your help.
The grinding noise is an electrical problem. Do not think it's mechanical just because it sounds and feels like it. There are several potential causes:
1. Motor connector not in far enough
2. Motor cable connectors at the controller end loose or not connected properly.
3. Melted connectors at the controller end
4. Damaged motor cable, especially where it comes out of the axle
5. Blown MOSFETs in the controller due to going too slow up a hill.
The worst thing you can do is continue to give power when you get the grinding noise. You start with a small issue, like 1 above, but if you keep trying when the motor can't turn, you get the consequential damage of 5 as well.
Check all the connectors and cable first, then we have to think about testing the MOSFETs.
Specially in relation to the earlier Swytch kits is the weird connection between the power-pack and the rest of the kit, it's very problematic and causes any of the above problems, which is why they abandoned it.