A crooked commercial overhead door often stops mid-cycle because the safety sensors detect an obstruction, even when nothing is in the way. This happens when one side of the door sags or binds, causing the door panel to tilt and interrupt the infrared beam between the sensors. The system interprets this tilt as a blockage and halts operation to prevent injury or damage. You’ll typically see the door rise unevenly, hear scraping or grinding on one side, and notice the sensor LEDs blinking or turning off entirely. Start by checking if the door moves smoothly when disconnected from the opener—pull the emergency release and lift it manually. If one side feels heavy or sticks, the issue is likely mechanical, not electrical.
Inspecting the Door Tracks and Rollers
Begin with a visual check of both vertical tracks. Look for gaps between the roller and the track flange—more than 1/8 inch indicates misalignment. Spin each roller by hand; if it wobbles or feels rough, the bearing may be failed or the shaft bent. Debris like gravel or packing material can lodge in the track, forcing the roller to climb out. Use a flashlight to examine the track’s interior for dents or bends caused by forklift impacts. Loose lag bolts securing the track to the wall jamb allow shifting over time; tighten them only if the track is already plumb—never force a bent track straight, as this can worsen the misalignment.
How Sensor Alignment Relates to Door Geometry
Safety sensors are mounted just above the floor on either side of the door opening. They require a clear, unobstructed line of sight. When the door tilts due to a sagging panel or uneven lift, the bottom edge of the door swings inward or outward on one side, breaking the beam. This is especially common on wide doors where the center sags, pulling the sides out of square. Measure the gap between the door bottom and the floor at both ends—if it differs by more than 1/4 inch, the door is not level. Use a long level on the bottom rail to confirm. Never adjust the sensors to ‘see’ through a tilted door; this defeats the safety function and risks entrapment.
When Rollers or Hinges Are the Culprit
Worn rollers with flat spots or seized bearings cause sticking, particularly in high-cycle doors. Nylon rollers degrade over time; steel rollers can corrode in damp environments. Check the hinge bolts where they attach to the door sections—elongated holes indicate the hinge has pulled loose, allowing the section to shift. Replace damaged hinges with the correct gauge for your door’s weight. If rollers are binding in the track, lubricate them with a silicone-based spray—never use grease, as it attracts dirt. If the roller shaft is bent or the hinge is torn, replacement is required; these are not adjustable components.
The Role of Torsion Springs and Cable Drums
If the door is difficult to lift manually and stays crooked throughout its travel, the torsion spring system may be at fault. A broken spring on one side creates uneven torque, causing that side to lag. Inspect the spring above the door—look for a gap in the coils, which indicates failure. Also check the cable drums on each end of the shaft; frayed cables or loose set screws allow the drum to slip, creating imbalance. **Do not attempt to adjust or replace torsion springs.** They store lethal amounts of energy and must be handled only by trained technicians with proper winding bars and safety equipment. Cable inspection is safe, but any spring work requires professional service.
Checking Sensor Wiring and Power
Although mechanical issues are more common, electrical faults can mimic alignment problems. Verify that both sensor LEDs are lit steadily—one green, one amber or yellow, depending on the model. If one is off or blinking, check the wiring for staples crushing the conduit, rodent damage, or loose connections at the sensor or opener terminal. Use a multimeter to confirm 12-24V AC at the sensor wires. Clean the sensor lenses with a dry microfiber cloth—dirt or condensation can weaken the signal. Never bypass the sensors; doing so violates safety codes and removes critical protection against entrapment.
Frequently Asked Questions
### Can I realign the door tracks myself if they’re loose?
You can tighten loose lag bolts if the track is already plumb and undamaged, but never attempt to straighten a bent track or force it into position. Over-tightening can twist the track further, and incorrect alignment worsens roller binding. If the track shows dents, bends, or torn metal, it needs replacement.
Why do the sensors work fine when the door is closed but fail when opening?
Sensors only need to be aligned when the door is moving through their beam path. A door that sags in the middle or tilts on one side only interrupts the beam during travel—when closed, the bottom seal may sit level and not block the sensors. This is why the fault appears intermittently during operation.
Is it safe to disconnect the opener and operate the door manually to check for crookedness?
Yes, pulling the emergency release cord and lifting the door by hand is the safest way to assess balance and binding. Do this only when the door is fully closed. If it’s hard to lift, uneven, or drops quickly, do not operate it further—call a technician, as spring or cable failure may be present.
