Garage door opener chain sags significantly or slaps against the rail during operation.

Safety first: Unplug the opener before adjusting chain tension.

Steps to adjust:

• Locate tension adjustment: On the Motorlift rail near the trolley, find the chain tension bolt and nut assembly.
• Tighten chain: Turn the adjustment nut to tighten the chain until it hangs about 1/4 inch below the rail at midpoint. Do not overtighten, as this can damage the sprocket and motor.
• Inspect sprocket: Check the drive sprocket on top of the opener for worn or sharp teeth. Replace the gear and sprocket assembly if worn.
• Lubricate chain lightly: Apply a small amount of garage door lubricant to the chain to reduce noise and wear.