Opener attempts to move the door but stops almost immediately and shows E4; motor hums briefly or does not run at all.

Safety first: Isolate mains power before removing the opener cover. Do not operate the door with the motor cover removed.

• Check door moves freely: Release the emergency disconnect and move the door by hand. If the door is stiff, correct the mechanical issue first (rollers, tracks, springs).
• Inspect drive system: With power OFF, remove the opener cover and inspect the chain or belt and drive sprocket. Ensure the chain/belt is not jammed around the sprocket or guide. Adjust tension so there is a small amount of slack; do not overtighten.
• Check motor capacitor (if fitted): Many Cardale AC openers use a cylindrical start/run capacitor mounted near the motor. Look for bulging, leaking, or burnt smell. Discharge the capacitor safely, then replace it with an identical µF rating and voltage if suspect.
• Spin motor shaft by hand: With power OFF and belt/chain removed if necessary, try to rotate the motor shaft. If it is seized or very stiff, the motor is likely failed and must be replaced.
• Reset overload: Some models have a thermal overload that resets after cooling. Allow 20–30 minutes, then restore power and test. If E4 returns immediately, replace the Cardale drive motor assembly or complete head unit.