Opener runs but door does not move; trolley may not engage; four flashes or code “4” on Decko opener LED.

Safety first: Ensure the door is in a stable position and will not fall. Disconnect power before working on the rail or trolley.

Check trolley engagement:

• Locate emergency release: The red release cord hanging from the trolley disengages the door from the opener.
• Re-engage trolley: With the door in the closed position, pull the release cord toward the opener head (or in the direction indicated on the label) until it clicks back into the engaged position.
• Test movement: Restore power and run the opener. The trolley should now move with the door attached.

Inspect trolley and rail:

• Check for damage: Look along the Decko rail for bends, dents, or obstructions. Inspect the trolley carriage for cracks or stripped teeth (on chain/belt drive models).
• Check chain/belt tension: For chain or belt models, the drive should sag about 1/4–1/2 inch at mid-span. Adjust the tension nut at the trolley end if it is excessively loose or tight.
• Lubricate rail (if chain drive): Apply a light coat of garage door lubricant to the top of the rail where the trolley slides (do not lubricate the belt).

If the trolley is cracked or stripped, replace the trolley carriage assembly compatible with your Decko model.