Shimadzu LC-2010C HT Pump Problems: High Pressure, Fluctuation and “No Pump Home” — Analytical Instrument Guide

The pump is the heart of an HPLC. If the heart keeps beating, the body keeps working — and it is exactly the same here. The pump pushes solvent forward, the solvent carries your sample into the column, separation happens, and the detector finally gives you a result.

If the pump stops, nothing moves. No flow, no separation, no peak. That is why stable pressure is the single most important thing to watch on an LC-2010C HT — and why most of the service calls we get on this instrument come back to the pump.

This is what we check, in the order we check it.

High pressure — start at the filter

High pressure is the most common pump error on this system. Work from the easiest thing to the hardest:

• Line filter blocked. This is the first thing to look at, every time. A blocked line filter raises pressure on its own and is cheap and quick to change.
• Check valve worn or dirty — both inlet and outlet. A bad check valve does not usually fail cleanly; it shows up as pressure fluctuation rather than a hard stop.
• Pump seal worn. A worn seal leaks from the pump head. The solvent that should be going forward does not, so you lose flow and the pressure reading goes wrong.

If you see the pressure moving up and down instead of sitting steady, think check valve, line filter, pump seal — in that order.

Air bubbles — the solvent is not moving

A trapped air bubble stops solvent from moving forward. The tell-tale sign is that purge does not work properly — you purge, and the line still does not clear.

Degas the mobile phase properly and purge again before you go looking for a mechanical fault. Many "pump problems" are only a bubble.

"No pump home" — the sensor that counts

This is a physical error, and it is worth understanding how the system actually knows the pump is turning.

Open the left side panel of the pump section. Inside you will find a black disc with a cut-out in it, and a sensor sitting over that disc. The sensor is U-shaped — light goes across the gap from one arm to the other, and the disc passes between them.

Every time the cut-out goes past, the sensor counts it. The speed of those counts is how the instrument measures flow — at 1 mL/min the disc should be turning at a specific rate. The instrument checks this count on every cycle before it lets the run continue.

The day it stops counting — either because the count is missed, or because the motor never turned at all — you get "no pump home."

Four things to check, in order

1. Is the disc rubbing the sensor? The disc must pass exactly in the centre of the sensor gap, with clearance on both sides. If it is rubbing, it can damage the sensor outright, or slowly coat and block the light hole. A blocked light path means the sensor stops working even though nothing looks broken.

2. Is the sensor itself dead? Sensors fail. If the disc is turning cleanly and centred, and there is still no count, suspect the sensor.

3. Is the pump drive board passing the signal on? The sensor may be counting correctly and the signal may still not be reaching the main board. That is a drive board fault, not a sensor fault — and it looks identical from the front panel.

4. Is it the main board? The LC-2010 main board is difficult, and it carries a lot of different faults. In our experience, if the mechanism and the hardware are fine, most pump errors on this instrument end up at the main board. A failed IC there can stop the pump from moving at all — and then of course the sensor never counts, and you see the same "no pump home" error.

So for a pump that will not move, there are three real possibilities: main board, sensor, or pump drive board. They produce the same message on the screen. Telling them apart is what the service visit is for.

Quick reference

What you see	Look at
High pressure	Line filter → check valves → pump seal
Pressure fluctuating	Check valve, line filter, pump seal
Purge not working	Air bubble — degas and purge again
No pump home	Sensor alignment → sensor → pump drive board → main board
Flow low but pressure normal	Pump seal leaking at the head

Before you call us

Three things you can check yourself in ten minutes, and they resolve a good number of cases:

1. Change or clean the line filter 2. Degas and purge properly 3. Open the left panel and look at whether the disc is centred in the sensor gap

If the pressure is still unstable, or you are seeing "no pump home" after that, the fault is deeper — sensor, drive board or main board — and it needs someone with the parts and the meter in hand.

We service Shimadzu LC-2010 and LC-2010C HT systems across Maharashtra and Gujarat, and we carry the common pump spares.