How to inspect and clean e-bike and e-scooter connectors

Turn the bike off, remove the battery, then press and hold the power button to drain leftover power, as Rad describes (Rad: bike won't turn on). Bosch also says to take the battery out before any work on the bike, because the system could switch on by accident (Bosch Performance Line CX manual).

Lectric explains that each part, such as the motor, pedal sensor and display, has a quick plug on its cable that leads to the controller, and some sit under plastic wrap. Rad's guide lists the order it checks them in: display, rear and front brake, throttle, headlight, motor, taillight, battery, pedal sensor and the main harness. If you need slack, Rad says to snip nearby zip ties with flat-side cutters.

Before you unplug, check that the arrows on the outside of the plug line up, and take a photo if they do not (Rad). Pull the two halves straight apart without twisting (Rad, Lectric).

Use good light and look for:

• Bent, broken or dirty pins. Rad says the pins must be clean and straight.
• Moisture or debris inside the plug.
• Corrosion, a cracked shell or damaged cable insulation, which Bafang lists in its speed sensor fault sheet (Bafang error 21 solution sheet).
• Anything that looks melted, scorched or smells burnt. Treat that as a stop sign.

• Rad says never to put tools into a connector, never to touch the pins with metal tools, and never to try to straighten a bent pin, since that can cause permanent damage or injury.
• If the battery terminals are damp, Rad says to let them air dry completely before you put the battery back.
• Rad says not to clean or repair dirty or damaged battery terminals yourself. Take a photo and contact support instead.
• Use only the cleaning method your own maker gives. Shimano says to clean a charging connection terminal with a clean rag or cotton swab dampened with ethanol (Shimano E-BIKE FAQ). Bosch says to clean its battery plug poles now and then and lightly grease them with technical petroleum jelly (Bosch battery safety). Yamaha says not to grease its battery terminals at all (Yamaha e-bike FAQ). Because makers differ, do not borrow one brand's method for another.
• Bosch also warns against spraying the battery with water or using a pressure washer.

Line up the notch inside, the pins and the outside arrows, then press the halves straight together without twisting (Rad). On a Lectric motor cable, the plug does not click, so press it in firmly and make sure it is fully seated. On Rad bikes, the threaded display plug screws together.

Put the battery back, turn the bike on and test it. If the problem is still there, power off, remove the battery, drain leftover power and move to the next connector (Rad). When you are done, replace any zip ties you cut so cables cannot rub or snag.