Troubleshooting: Scooter display that turns off or shows incorrect information

A display that remains black, turns off while riding, restarts on its own, or displays nonsensical values is not always faulty itself. It's the end of a long chain: a cable running down the column, connectors, a power supply provided by the controller, and a data connection. Most often, it's this chain that fails. This guide shows you how to check each component individually.

What the display does, and why it's fragile

On most electric scooters, the display does much more than just show the speed. It often serves as a power switch, transmits settings (mode, maximum speed, start-from-a-roll), and, on some models, reads the throttle input before sending the command to the controller.

To achieve this, it is connected to the controller via a multi-wire cable: power, ground, ignition wire, and one or two data lines. This data travels via a serial connection or a communication bus, such as the CAN bus. The cable runs inside the steering column, bends with every fold of the scooter, twists with every turn of the handlebars, and is exposed to water that runs down the tube. This is a weak point in the system. Our guide on the operation of the display details its role.

Symptom 1: The display no longer turns on at all

If nothing turns on, neither the screen nor the lights, the problem could be with the battery as much as with the display. First, follow our troubleshooting guide for a scooter that won't turn on.

If the battery is outputting the correct voltage and everything else seems to be powered, then check the following:

• The display connector, located under the handlebar or within the deck: may become disconnected due to a fall, have a pin pushed out, or experience green oxidation;
• The cable at the folding hinge: pinched sheathing, exposed wire, blackened copper;
• The button: On a display that also serves as a power switch, a broken or wet button will prevent the device from turning on.

Symptom 2: The display turns off or restarts while riding

Observe whether the display turns off on its own or along with everything else. If it turns off along with the motor and lights, and you sometimes have to plug in the charger to get it working again, it's usually the battery that's cutting out. Our guide on "scooters that cut out while accelerating" addresses this issue.

If it restarts on its own, similar to what happens after pressing the power button, consider a faulty connection in the power or ignition wire. The test: place the scooter on its kickstand, lift the wheel, slowly rotate the handlebars from one stop to the other, and gently flex the steering column. If the display flickers or restarts at a specific position, it indicates a problem with the cable at that location.

A power supply that drops significantly during acceleration can also cause the display to restart. This could be due to a faulty battery connector or a battery that collapses under the strain.

Symptom 3: Absurd values or communication error code

Erratic speed readings, inaccurate battery level displays, settings that reset, or communication error codes: the display is not receiving data correctly from the controller, or has stopped receiving it altogether.

• Data line interruption or interference: Similar vulnerability in the motor cable; a partially severed data wire can produce inconsistent values before completely cutting off.
• Humidity: Water that gets between the display and its circuit board, or into a connector, can cause current leakage between adjacent wires. This is a common cause of problems after rain.
• Incompatible display and controller: After a replacement, a display from a different version may not be compatible with the controller.
• Wheel or motor pole size adjustment: An inaccurate but stable speed often results from incorrectly entered wheel diameter or motor pole parameters, rather than a malfunction.

On a Dualtron scooter, our guide to error codes and symbols helps you understand what is displayed.

Multimeter tests

With the display disconnected, and the scooter powered on (if its wiring allows), you can check at the connector on the controller side to ensure that the display is receiving power. You should look for a stable voltage, close to the battery voltage for displays powered directly by it, or a few volts for displays powered by a reduced voltage. The manufacturer's wiring diagram indicates which wire carries which signal; without a diagram, do not take measurements randomly.

With the scooter turned off and the battery disconnected, test the continuity of each wire in the cable, from one connector to the other, while moving the cable. A beep that stops indicates a damaged wire. Keep in mind that some of the wires in this cable carry the full voltage of the battery: use insulated probes and never create a short circuit between two pins.

Repair or replace

A severed column cable can be replaced or repaired with heat-shrink tubing protecting the soldered joints, ensuring a sufficient cable loop at the hinge. An oxidized connector can be cleaned if the pins are intact; otherwise, it should be replaced. A display unit whose circuit board has been exposed to water may function again after complete drying, but oxidation often continues its work: a display that malfunctions again a few weeks later should be replaced.