Error 3 or 4 on HTEC-500/510 pump with acetate in the mobile phase
High concentration of acetate becomes a cause of trouble on our small check valves. The balls and seal in the valve can be coated by the layer of acetate residue which is like jelly. This can be fixed by washing with water then switch to acetone for 30 min each. Please consider lowering the acetate level in the mobile phase.