Opener runs but door does not move, display shows code 8 or flashes eight times.

Safety first: Keep clear of the door while testing. Disconnect power before handling the chain/belt.

• Check emergency release: Ensure the red release cord has been pulled back toward the opener to re‑engage the trolley (on many Merlin models you must run the opener until the trolley clicks back into the carriage).
• Inspect trolley carriage: Look at the carriage on the rail. If it is cracked or missing teeth, it will need replacement.
• Check chain/belt: Remove the opener cover and inspect the drive sprocket. Verify the chain or belt is on the sprocket and properly tensioned. Refit and tension according to the Merlin manual (usually 6–12 mm sag at mid‑span).
• Inspect drive gear: On some Merlin units, a plastic worm or helical gear inside the head can strip. Look for plastic shavings and a free‑spinning motor shaft. If stripped, replace the gear kit.
• Test operation: Restore power and run a full cycle. If the trolley still does not move with the motor, the carriage or internal gear set must be replaced.