What are Channel A and Channel B?

Hi Bill,

It’s possible that there is debris inside the laser counter (channel A) that is blocking particles from moving through or covering the lens. We recommend cleaning the sensor: Sensor Maintenance. As blowing air through the air channel can can the fan to move too quickly, causing damage, we recommend that you apply short bursts of air or use a toothpick to hold the fan in place.

If this doesn’t work, you can also replace the laser counters.