Error: Sample syringe h/w lost steps

I am continuously getting this error (files attached) where i did many things, like Prime sample syringes & prime wash syringes.... with Waters recommended wash solvents....even reseting system(SM) many times... even reset main SM power.... but still this error occur just after emptying sample syringe...(just after injection run) Can i have to re-install sample syringe, sample needle etc. again....?pls suggest me with complete details....!! bcuz I cant trust Waters Agent here in Doha, i am doing all my UPLC troubleshooting by my self....this service engineer has no UPLC maintenance experience. Note: do I have to replace solvent filters of SNW&WNW? may be SFs clogged.(but this error at last step of injection)Regards.~Salman


  • Salman,

    It is likely that the Sample Syringe Pulley and Belt Drive may have slipped, this would result in a higher frictional force that would Motor may not be able to overcome. A Field Service Engineer may be required to verify this theory and repair as needed.

    - Dave D.

  • Dear Dave D,

    Thanks for your answer, my problem has resolved by this trick....> First i checked fluidic lines, any dust or leakage or loose fittings, moved motor pulley… all feels to me ok, and after that I start all diagnostic test of SM (pls checked attached file)… all test Passed….

    Before injection, I prime the sample syringes by (MeOH:H2O:IPA)=702010 for SW & (MeOH:H2O)=60:40 for WW,,, 4 cycles & leave the syringe draw rate as default “automatic” (100uL)…. & also continuously observes any leakage or disturbance in motor movement … but seems all ok…

    Now no error, for more confirmation I inject my sample 10 times… nothing happens.

    May be this error due to In-correct syringe draw rate?

    I'm still tending to think about a mechanical problem somewhere on the syringe drive mechanism, because our Waters Service Manager_Dubai, suggest me to inject samples with higher syringe draw rates then observe.

    Is this possible you guide me more how to check mechanisms of Sample Syringe Pulley and Belt Drive , any documents, video or flow diagrams to diagnose the real problem?

    ~ Salman

  • Hello Salman,

    Since the most likely mechanical component to concentrate on is the Pulleys/Belt due to frictional overload, I suggest to inspect these items. This will be very simple, I have attached some photographs of what you will need to focus on. If they are out of alignment it is likely the cause of the intermittant errors.

    Best Regards,


  • Here are the photo's.

  • I am attempting another file attachment for this posting.

  • Thanks Dave,

    This is the right picture, I’m waiting for long time, yes, you are right some problem in drive/belt pulley... at this time our UPLC is fine but still at higher syringe draw rate (like 150 or 200) sometimes it stuck.... I inspected as described in the picture & removed some dust by blower, but I will appreciate if you explain in detail how to inspect all parts & also provide more service pictures & manuals of SM ... to avoid further error; as we have bulk of samples through out the day.


  • Hello Salman,

    Beyond the Operators Guides (provided with the instrument and located on line) and the ACQUITY On-Line help Waters does not have any other user available documentation, therefor my provision of the photo's I have provided. The other best advice that I can give if you suspect the drive mechanics is (with the instrument powered off) to manually rotate the pulley to determine if excessive mechanical friction may be present, if that is the case a Feild Service Engineer would need to visit for replacement or for further evaluation.

    However, there is a very good chance that the mechanics are in good condition. Solvent dependant viscosity and fluid movement theory could explain an possible hydraulic lock up which would cause the mechanics to be unable to overcome the fluid movement. Therefor the syringe draw rate may need to be adjusted as you may have discovered. The purpose for setting/programming the syringe draw rate was built into the product to allow choosable values, you may need to run at a lower draw rate.

    Best Regards,


  • Thanks Dave for your great support, you are right it should be too much torque on syringe drive/pully movement or some solvent viscosity issue, and or might be optical sensor is dirty or somehow defective. what you think ?

    At the end i can say, in future we will manage this issue at lab level. I am also sharing one more file with our community memebers, in which all SM fluidics parts are clear to observe.

    Kind regards.


  • I just wanted to say that this post was valuable to solve my problem.  I had the exact error message. Acquity Operator's guide didn't help at all. After reading this post, I reduced the syringe draw rate to 50 and that solved the problem! My solutions are in 100% aqueous so I guess that caused the frictional overload. Which is surprising that I've made lots of 100% aqueous injections on 717 AS and never had such problem but I guess Acquity is that much sensitive. I wonder what was the original poster's solvent for the sample solution... Anyway, thanks!!

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