After updating firmware (particularly to v3.9.1), some users encounter Carrier Board Fault 9 on startup. The robot won't initialize and shows this error persistently. Here's a quick hardware fix that has been confirmed working by multiple community members.

When does this happen?

  • Most commonly reported after upgrading from 3.8.x to 3.9.0 or 3.9.1
  • Can also appear after a power outage during normal operation
  • The error persists across reboots — simply restarting the control box does not clear it

The fix: tap the safety relays

  1. Power off the control box completely and unplug it
  2. Open the control box enclosure (remove the cover screws)
  3. Locate the safety relays on the main board — these are small rectangular components, usually blue or black, near the safety circuit area
  4. Gently tap each relay 2-3 times with your finger or a non-conductive tool
  5. Close the enclosure
  6. Power on and restart the control box

This clears the error in most cases. The root cause appears to be a contact sticking issue in the safety relay circuit that can be triggered by the electrical transients during a firmware update.

If it persists

  • Try the tap procedure again — sometimes it takes 2-3 attempts
  • Check that all board connectors are firmly seated (they may have loosened during the update vibrations/handling)
  • If the error still won't clear, the relay contacts may need professional cleaning or the relay itself may need replacement. Contact your distributor for warranty support.

Prevention

Before firmware updates, ensure the control box has stable power supply. Avoid updating during electrical storms or from outlets with known power quality issues. Always use a laptop (not teach pendant) for firmware updates — teach pendant updates have known bugs that can cause additional issues.

Internal hardware note

For reference: some older control boxes (2021-era) use a Raspberry Pi 4 Model B Rev 1.4 as the main CPU, with soldered (non-removable) memory. The board layout may differ from newer QNX-based controllers — relay positions will vary. Look for the rectangular components near the power input section.