This replacement component is a Standard Balboa M7 heater sensor featuring a 24 inch wire length. The assembly includes the sensor wire, electrical connector, and secure screw-down cap. Please note: the sensor tube and side mounting bracket are NOT included with this part. In most installations, you'll simply reuse your existing mounting hardware, eliminating unnecessary waste.

This sensor is commonly needed when your Balboa M7 control system displays an SN error code, indicating a sensor malfunction.

Troubleshooting OH Code with Cool Water:

If you're seeing an OH (overheat) code but your spa water feels cooler than 110°F, here's what's likely happening: Your M7 system uses dual sensors positioned at both ends of the heater tube. Rather than relying on a pressure switch like older models, the M7 controller verifies water circulation by measuring the temperature difference between these two sensors.

When the heater fires, the system expects to see a temperature increase between sensors, confirming proper water flow. If your pump isn't functioning correctly, water remains stagnant in the heater tube. The controller will cycle the heater on and off repeatedly trying to detect flow. Each heating cycle raises the tube temperature further until it eventually triggers the OH safety code and shuts down until manually reset.

In this scenario, your sensors are actually working correctly by detecting genuine overheating—the root problem is with your circulation pump operation. Investigate pump performance first before replacing sensors.

Additional tip: Overheat codes can also result from excessive filter cycle settings during warm weather or indoor installations. Never exceed F2 filter cycle frequency in hot ambient conditions.