Hot tub sensor swap

As I mentioned on the May Long weekend post I had to change the sensors on the hot tub.  I wanted to break this post out just so that people can find it in the future for those that are interested. I have a Polar Spa hot tub that is over 6 years old.  The name plate is wore a little and the model and dates are no longer present.  It is controlled by a Balboa M-series controller.

On the Friday of the May long weekend I opened up the hot tub to see a sensor error (code Sn).  This means that there is an error between the Sensor A (the inflow sensor) and Sensor B (the outflow sensor).  I called my hot tub guy up to find out what I could do about this.  Kyle over at J&J Service Tech in Calgary is a fantastic guy and answers my questions whenever I have them.  Kyle told me to shut the power off for 30mins to see if it would reset.  After the alotted time was over I turned the power back on and I got a Sensor B error (code Sb).  This code states that there is a malfunction with that sensor.  With another quick chat with Kyle and I found out that he did not have any sensors left as it is a busy time of year for getting hot tubs operational.  He suggested a few places that I try that I might find them.  He told me the part that I was looking for was the M7 Sensor.

Armed with my knowledge I set out to find the sensors.  After a quick google search and some waiting for stock checks I found some.  I figured if I was going to change one I might as well change both.  I drained the hot tub to below the heating tube.  You do not need to completely drain the hot tub, just make sure the water line is below where you are working.  I pulled the cover off of the controller and traced the lines from the sensors to their connection points on the board.  The circuit diagram is printed on the inside of the controller cover, and I always double check what I am working on is what the diagram says it is. 

Here are where the two sensors are located at.

Change the sensors was easy, just unthread and unplug them .  Then thread in the new one and plug it in the correct spot on the board.  I tucked the wires out of the way and put the cover back on.  I refilled it and turned the power back on.  It takes a minute for it to initialize then it indicated that it was operating correctly.

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