Opener will not run; control board LED blinks 3 times repeatedly.

Safety first: Disconnect power. Ensure the door is supported and cannot fall unexpectedly. Do not work under an unsupported door.

• Check door balance: Pull the emergency release and move the door by hand. It should lift smoothly and stay halfway open. If it is heavy or binds, have the door springs and hardware serviced before adjusting the opener.
• Inspect tracks and rollers: Look for bent tracks, damaged rollers, or obstructions. Clear debris and correct any obvious misalignment.
• Reset travel limits: Restore power. Follow the Mighty Mule manual to reprogram open and close limits using the limit set buttons or dials on the head unit. Ensure the door stops just at the floor and just at the header.
• Adjust force settings: If the opener reverses before closing, slightly increase the close force adjustment on the control board or housing, staying within manufacturer recommendations.
• Inspect limit mechanism: On chain or belt models with mechanical limit nuts, check for stripped or cracked limit nuts and damaged limit switches. Replace the limit assembly if it cannot hold adjustment.