When the conductivity reads “0”

For our Model 1575e and Model 140 controllers, we get calls with this status fairly often. Cooling tower conductivity sensor troubleshooting is something we do every day. In the end, most of the time you just need to initialize the calibration – and the root cause was probably too many calibrations being performed with a dirty sensor or system. Basically, the controller has been told too many lies about the signals it has been receiving!  Here are some practical things you can do in the field to fix a conductivity reading of 0.

0 Conductivity Display

When this occurs, there are several possible causes.

1- There is no flow in the system.

Solution: restore flow past the sensor! Check for debris in the plumbing or a closed valve. Clean the flow sight / float if needed.

2- The sensor is completely scaled over.

Solution: remove scale from the sensor tips with a wire brush, clean the sensor with dilute HCl.

3- A sensor wire has come loose.

Solution: check and tighten wires along the controller terminal blocks (right side inside the cover.)

4- The sensor tips are broken within the sensor.

Solution: Replace the sensor.

5- The controller is no longer accepting a conductivity input.

If after checking numbers 1-5 and you still have a conductivity of “0”, pull the sensor wiring terminal block off the controller. Turn it 180 degrees so that the wires are on the left side of the block. Re-install the terminal block. The Temperature Compensation thermistor will simulate a conductivity input of about 2000µS.

      • If you are in the ballpark of 2000, then your controller is responding correctly, and your problem is either in the sensor or the wiring. Be sure to flip the terminal block to the correct orientation right away.
      • If the controller still reads “0”, it brings us to #6.

6- The controller has been calibrated to “0”.

The answer is to initialize the calibration. In the main menu follow these steps:


This will wipe out all calibrations for conductivity on the controller and give you a fresh start. At this point, the controller should be reading conductivity, and it is safe to calibrate your controller.

90% of the calls we get regarding a “0” reading end up being a calibration issue.

If the controller still reads “0” after initialization, be sure to call Lakewood, we will talk you through next steps to troubleshoot your cooling tower conductivity sensor!