A static red line on the sidecar's LCD for an Htek UC924 phone is likely a hardware issue with the expansion module's display or connection.

The following steps can help determine if it's a minor connection problem or a permanent hardware failure. 

Initial troubleshooting steps

1. Power cycle the devices: Turn off and unplug the Htek UC924 phone and the sidecar from their power source. Wait 30 seconds, then plug in and power on the devices again. This can resolve temporary display glitches.
2. Check the ribbon cable connection: The sidecar connects to the main phone with a ribbon cable. Follow these steps to ensure the connection is secure:
   • Disconnect the sidecar from the phone.
   • Carefully inspect the ribbon cable and its port on the phone and the sidecar for any damage, bends, or debris.
   • Reconnect the sidecar, ensuring the cable is fully and securely inserted into both ports.
3. Test a different sidecar (if possible): If you can access another compatible sidecar, connect it to the UC924 phone. If the replacement sidecar works correctly, the original sidecar's hardware is the issue. If the problem persists with the new sidecar, the main phone itself may be causing the issue.
4. Try the sidecar on a different phone: If you can access another UC924 phone, connect the problematic sidecar to it. The sidecar is defective if the red line appears on the new phone. If the sidecar works correctly on the new phone, the original UC924 phone is likely the source of the problem. 

Possible causes for the static red line

• Faulty ribbon cable: Over time, the connection between the sidecar's LCD and control board can become damaged or loose, causing display issues.
• Physical damage to the LCD: The LCD panel could have damaged pixels or liquid crystals. This is a permanent hardware failure that requires replacing the unit.
• Loose internal component: The connection to the LCD panel on the sidecar's circuit board may have become loose.
• Logic board malfunction: A component on the sidecar's logic board that controls the display could have failed. 

What to do next

If the initial troubleshooting steps do not resolve the issue, the sidecar most likely has a permanent hardware fault.

• Under warranty: If the device is still under warranty, contact support for a replacement.
• Out of warranty: Replacing the sidecar is typically the most cost-effective solution if the device is out of warranty. Attempting an internal repair is difficult and often causes further damage