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Troubleshooting

Rad Power Bikes RadCity 5 Plus: error 30 or won't power on

On the 2021 RadCity 5 Plus, an error code on the Rad UI or a bike that won't turn on usually traces to a connector that vibrated loose. Rad's guide walks from the display plugs to the harness and battery connectors.

Last edited Nov 8, 2026 by Pedalwise team Edit History Add a subpage

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Tools

Parts

  • Zip ties
  • Replacement accessory or cable (through Rad support)

Your RadCity 5 Plus shows an error such as error 30 on the Rad UI Display or Remote, or it won't turn on. Rad's RadCity 5 Plus (2021) connector check guide says these usually come from a connector that has vibrated loose or been damaged. The short answer: check the display and remote plugs, then the wiring harness connector behind the seat tube, then the battery connector, then isolate each accessory.

This is wiring work. Take the battery out and drain residual power before every unplug. Rad says not to clean or repair the battery or mount contacts yourself. Stop and contact Rad support or a shop if you find damage.

Most likely cause

Error 30 is Rad's communication error between the display and controller. On its newer color display bikes Rad lists the causes as a loose connector, a damaged cable or a faulty controller (Rad code table), and the RadCity 5 Plus guide is built around the first of these.

Other causes to rule out

  • Damaged, dirty or wet battery or mount contacts. Photograph them and contact support. (Rad)
  • A faulty accessory, light, brake sensor or throttle. Rad has you unplug each one in turn. (Rad)
  • Some RadCity 5 Plus bikes have a jumper cable at the display. Rad's guide has separate steps for bikes with and without it.

How to confirm

  1. With the battery removed, inspect the battery and mount contacts and photograph them.
  2. Bikes with a jumper cable: check the accessory port on the jumper cable, then the Rad UI Display to jumper cable, Display to Remote, and jumper cable to wiring harness plugs. Photograph the arrows before you unplug.
  3. Bikes without a jumper cable: check the Rad UI Display to wiring harness and Display to Remote plugs.
  4. Wiring harness connector behind the bottom of the seat tube. Rad says to partly loosen the four outer cover bolts and turn the handlebar left for slack, and to check the bar turns fully both ways before you tighten the cover again.
  5. Battery connector. Rad's guide removes the four inner cover bolts and the two Phillips battery mount bolts, then the mount. When refitting, thread bolts partway before tightening, as Rad describes.
  6. Isolation checks, one at a time with the part unplugged while you power on: left crank pedal assist (orange), motor (black), taillight (blue), accessory connector (black cap), each brake connector (red), throttle (orange), front accessory port (black) and headlight (red).

At each plug, pull straight apart, look for damage, dirt or moisture, then line up the notch, pins and arrows and press together. Reinstall the battery and power on after each one.

Fix options

Reseat the connectors (easy)

Rad's tools: flat side cutters, a 3 mm hex key, a Phillips screwdriver, zip ties and a camera.

Replace the faulty part (moderate, with Rad support)

If one isolated part clears the error, note which one and contact support. Rad asks for a video of the problem, your symptoms, the steps you tried and your photos.

Controller or display diagnosis (pro)

If nothing clears it, leave further diagnosis to Rad or a shop.

Parts

  • Zip ties
  • Replacement accessory or cable, only as Rad support directs

When to get a pro

Get help for damaged contacts or connectors, or if the error survives the full check. After any work, confirm cables clear moving parts and the handlebar moves freely. See inspect and clean connectors and e-bike won't turn on.

Sources

Stuck after these checks? Find a shop near you.

Need a pro?

If these steps didn't fix it, find a shop near you in our partner network. For battery or wiring trouble, look for shops marked Battery and electrical.

Talk

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