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OH and Temp Sensor Repair

Spas use TWO sensors. The Temperature and the Overheat or High Limit sensor.

Sensors basically change resistance values as the water heats or cools. The change in resistance tells the board the temperature of the water and the heater. If the sensor itself gives faulty or no resistance values, the spa will not operate or operates wrong. The board is smart enough that it will typically tell you by sensor error messages if the values are out of range by giving you a sensor error code on the topside.

The Temperature sensor must either be IN the water or IN a housing that is in the water. Most common design is in the water, usually where the filter resides. This sensor tells the board actual temp. If the topside reading on the board is off, then its usually this sensor (could be the board). If the board sees the water get too hot, it will attempt to cool the spa or shut down completely.

The OH or High Limit sensor has one purpose in life. It sits next to the heater and watches the heater closely. If the heater starts to overheat, the board sees the temp on the OH sensor and will shut the spa down. So if you get an OH error, either the heater IS overheating OR the sensor has failed.

A fault error code of --- is likely the temp sensor.