Inspecting air filter, common to the LNC head and the IC head;
1, Check to see if the air filter inside the filter box located on the front side of the head unit is not stained with your eyes.
    How to check if the filter is not stained:
    i, Select the <maintenance> command from the main screen, and then the <self calibration> command.
    ii, Next, select the <set-up group> command, and then the < vacuum calibration> command. 
    iii, If the calibration result has any problem, the message for asking you to replace the filter with a new one appears on the screen.
2, If the air filter is stained, replace it with a new one.

Steps of replacement of the head filter ( used the tool hexagonal wrench):
i, loosen the "setscrew" of the filter box to remove the " filter box U"
ii, Check to see if the filter is stained
iii, if it is, replace the filter of the filter box L with a new one
iiii, Insert the new filter into the filter box L securely and fix them with the setscrew. Check to see if the O ring is fit into the groove of the filter box L also.