Waters Alliance 2690 needle bottom sensor malfunction

[tony_herlt]

We are getting a needle bottom sensor malfunction message with the injector of a Waters Alliance 2690 HPLC system. There was no evidence of the needle being bent from hitting the bottom of the vials but for good measure the needle was recently changed and its travel set 2mm above maximum depth. However, the message still occurs every few hours of operation. Rebooting the Alliance system restores normal function for a few hours. Has anybody else experienced this problem and if so is it rectified by replacing the injector sensors? TIA, Tony.

[DR]

I think you have to clean up & lube the screws that drive the needle assembly to correct that error message. Evidently the motor(s) that drive the needle are sensitive to any changes in the torque required to move the carriage and error out with little provocation.