The speed is not working on my instrument, and/or the water temperature is incorrect

If the speed or temperature on your instrument display is not working (e.g. ST40, i40, ST60, ST60+, ST70, i50, i70, ITC-5), then it could be due to two common reasons.

Please perform the following check: Look at your speed instrument. For speed, is it showing dashes (-.- knots) or is it showing zeros (0.0 knots)?

• If it is showing zeros, the cause is probably the speed sensor. See the following FAQ to check if the speed circuit is working within the transducer: Testing an instrument speed through water transducer.
  
  
• If it is showing dashes, it could be because the thermistor has failed within the transducer, which also makes the water temperature incorrect (or shows dashes too). The instruments use the water temperature thermistor to detect whether there is a transducer connected or not, so no thermistor = no speed data.

The thermistor is measured between the brown and white wires on the instrument speed transducer. To test the thermistor, disconnect the brown and white wires from your instrument (or from the ITC-5), and then measure the resistance of the thermistor using a multimeter. You can measure either way round. If you have a manual-ranging multimeter, set it to the 20k (20,000 ohm) range.

Below is a table showing the approximate expected resistance values you should measure at various temperatures. 11K ohm is approximately 23°C. If the resistance is drastically different (e.g. measuring open circuit), then you have a failure with the thermistor water temperature element.

To get the water temperature working again, you will need to replace the transducer as these are fully sealed bodies and not repairable.