Canon NP6621 Service Handbook page 60

IMAGE FAULTS
14 The copy has a fixing fault.
Cause Step
Upper and 1
Lower
developing
rollers
Fixing roller 2
heater (H1)
Lower 3
fixing roller
pressure
Copy paper
3–14
Checks
Is faulty fixing occurring in the feed
direction of the paper?
Does the fixing roller heater (H1) go
ON immediately after the copier is
switched ON?
Is the nip width within the standard?
Yes/No Remedy
YES Check the scratches on the
upper and lower fixing rollers.
NO Refer to the sub-section
"Fixing roller heater does not
operate."
NO Adjust the lower fixing roller
pressure.
YES Check if the recommended
paper is being used. if the
results are satisfactory when
the recommended paper is
used,instruct the user to use
it.