Canon imagePRESS C800 Series Troubleshooting Manual page 195

Chapter 1
5) Using lint-free paper [1] moistened with alcohol, clean the Sensor Flag's surface side [A], back side [B], and the [C] part which comes in contact with the Fixing
Inlet Guide.
6) Clean the Separation Plate [1] for inner delivery Unit with lint-free paper [2] moistened with alcohol.
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