Possible causes: 

Poor connection between battery and controller

The battery voltage is low or the battery is faulty or disconnected

Poor connection between motor wires and controller

Motor fuse blown

DOSS physically disconnected

Faulty motor and DOSS assembly

 

Possible solutions: 

Ensure that the battery terminals are properly connected on both the controller and battery side

Measure the battery voltage – it should be no lower than 11V DC when placed under load.

Check for corrosive build-up around the battery terminals; if there is corrosion replace both the battery and battery terminals

Measure the onboard charger’s output voltage. It should be about 14V DC

Replace blown fuse. If it blows again, replace the controller

Disconnect the motor wires and reconnect, ensuring that the screws have been sufficiently tightened

Ensure that the DOSS cable is securely connected on both the controller and motor assembly side

Replace the battery

Replace faulty controller

Replace motor assembly