Opener will not run, 7‑segment display on head unit shows solid “1” immediately after power‑up and beeps once.

Safety first: Disconnect power to the opener before touching any wiring. Do not operate the door with the safety sensors bypassed except for brief testing, and keep people and pets clear of the door.

• Check sensor LEDs: On most Marantec photo eyes, one side is the sender (solid LED) and the other is the receiver (solid LED when aligned). If the receiver LED is off or flickering, alignment or wiring is suspect.
• Realign sensors: Loosen the wing nuts on each sensor bracket. Rotate and tilt the sensors so they point directly at each other at the same height, about 4–6 inches above the floor. Tighten the nuts and confirm the receiver LED stays solid when you gently tap the bracket.
• Inspect for obstructions: Remove any items, cobwebs, or debris in the beam path. Make sure the sun is not shining directly into the receiver; if it is, angle the sensors slightly or add a small sun shield.
• Check wiring: With power off, verify the low‑voltage wires from the sensors are firmly connected to the correct terminals on the Marantec head (usually marked for photocells or safety sensors). Look for staples piercing the wire, cuts, or corrosion at splices. Repair damaged sections and keep polarity consistent (same color wire to the same terminal on both sides).
• Test operation: Restore power and close the door using the wall button. The error should clear automatically when the sensors are aligned and the beam is unobstructed.
• If still faulty: Swap the sensors with a known‑good Marantec‑compatible photo eye kit. If the error clears, replace the defective sensor pair.