HTEC Pump Errors

Below are display errors for the HTEC-500/510, possible causes, and solution.

Error 1-Upper Pressure Limit Error

Cause: Pressure is higher than the set pressure limit.  Turn on pump and check the pressure display.

Solution: This is most likely caused by a clog.   Please see this article.

Error 2-Lower Pressure Limit Error

Cause: Pressure is lower than the lower pressure limit

Solution: This is most likely caused by a leak causing a drop in pressure.  Check fittings and tubing for leaks.

Error 3

The computer on the HPLC pump unit is programmed to display error 3 when one of the check valves

does not work properly. If the pressure sensor detects a rapid pressure decrease and cannot return the

pressure to the previous level within 12 rotations of the motor, error 3 is displayed. If you are running the

pump for maintenance, please switch off the pulse free mode.

Error 4

Error 4 is a motor rotation error due to an abnormal load or irregular rotation of the motor.


Error 3 or Error 4 may occur for the following reasons (Treatments are also described below):

    A. There is a leak somewhere in the high pressure zone between the pump piston and the separation column. Check if there is any leak in the flow line. Typically, the connection at an injector valve or at the column inlet may become disconnected. If you find it has been disconnected, please reconnect it. A pressure reading of more than 15 MPa will lead to the disconnection of fittings. Please check that your column is not too old and if the precolumn is clogged.

    B. Air needs to be removed from the pump. See chapter 8, page 11 of the HTEC manual.

    C. If air gets trapped in the pump frequently, make sure the connections are tight enough, tubing is not damaged,  and the elution degassing system is working properly (see also chapter 6,

page 7). The cause of resistance in the pumping system can be either that the mobile phase bottle

is at a lower position compared to the HTEC-500 or an inline filter is present upstream of the pump

(typically a tubing anchor filter in the mobile phase bottle is used). Check that the mobile phase

bottle is on the same level as the HTEC-500. Please remove the filter if you have one.

    D. One of the check valves has lint, dust or something inside. This problem happens more frequently in

the inlet check valves located at the bottom of the pump head. Replace only the inlet check valve

having the problem by the method described below. If the problem persists even after this

exchange, the outlet check valve may be the problem.


To find out which side of the pump has the problem perform the following steps:

  • Keep the mobile phase level in the bottle at the same level or a few inches lower than the inlet check valve.

  • Release both the left and the right side of the hex nut that holds the tubing at the outlet check valves and see if the mobile phase comes up and at what speed it comes up at. When one of the inlet check valves has failed, the mobile phase on that side should come up significantly slower than the other side or may never come up. You can also run the pump with the pulse free mode off to check if the solution flows or not.

  • Replace the failed inlet check valve with a new one (Inlet check valve, catalog #HT-IV).

  • Alternatively, the failed check valve can be cleaned but very detailed work is required to clean it well. 

  • Please also check if the degasser is working. The HTEC-500 does not have a degasser error indicator.  Please turn on the system power and listen for the noise of the degasser vacuum pump (buzzing noise). If the noise stops with in 3 min from system power on and then the restarts in ~3-5 min, it is normal.  If the noise doesn’t kick back on over 5 minutes, the degasser may require repair.  Please contact Amuza for further evaluation.

  • Washing the line may resolve pump issues.  First, please rinse the pump and line with water after removing all columns. Don't mix methanol and mobile phase in the line or pump as It may cause precipitates to form resulting in clogs. Then run pump with 100% methanol for one hour. 

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