Opener starts to move the door then stops and reverses; display shows “3” or three flashes; door may only move a few inches.

Safety first: Disconnect power and pull the emergency release to operate the door manually. Never place hands near springs or cables.

• Check door balance: With opener disconnected, lift the door by hand halfway. It should stay in place. If it slams down or shoots up, the springs are out of balance and a professional should adjust them.
• Inspect tracks and rollers: Look for dents, bends, or misalignment in the vertical and horizontal tracks. Ensure all rollers are inside the track and spin freely. Replace cracked or seized rollers and gently straighten minor track bends with pliers.
• Remove obstructions: Clear any debris, locks, or hardware that might catch the door. Check weatherstripping for binding.
• Adjust force settings: On the Marantec head, locate the up/down force adjustment controls (refer to your specific model manual). Increase the closing or opening force slightly (1 step at a time) and test. Do not over‑increase; the door should stop and reverse if it hits a solid object.
• Re‑engage opener and test: Reconnect the trolley to the door, restore power, and run a full open/close cycle. If the error persists with a free‑moving door, the motor control board may be misreading force and require replacement.