Dear Chris,
N2324 and N2325 are for nozzle down sensors. THese sensors are located on the left and right side of the left and right walls of the head assembly respectively. There are very small holes in the walles through which these sensors transmit and receive the beams. THe procedure is the open the front cover the of head assembly, clean these 3 tiny holes (in an traingular pattern) using air. You can use a sharp pin to clean the hole to but be very careful not to damage the sensors.
If the holes are partially blocked then you can adjust the senstivity of the sensors using the potentiometers on the cable. The cable is on top of the head assembly (green colored potentiometers).
Hope this helps.
Vinit
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