Depress the reflux pedal. Check, that reflux valve opens.
Check, that fluid runs out of the instrument. If not, detach the instrument to see if fluid flows from the tubing, indicating a clogged instrument that needs cleaning.
Set Flow Rate 20 ccm, Vacuum Limit 500 mmHg. Dip instrument in water and depress main foot pedal to activate pump. If vacuum rises to the limit there is an occlusion in the aspiration path. Clean the instrument or change the fluid lines.
Check the pressure transducer – should show zero +/-5 when open.
Check for a clogged hand piece.
Check that reflux valve is working.