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"Sn" Error code ruing my life!


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I've been getting a "Sn" error code on my clearwater spa and I've spent the last few hours trouble shooting it and I'm not compltely sure what the problem is.
I've tested the resistance between the two temp sensors (if I understand correctly, one is high limit sensor and one is a temp sensor) and they both come in at a similar ohms rating. So I don't think they're damaged, but yet I'm still getting the error. Should I replace them anyway? Or is there a different part that is the culprit? I'm lost, please help!
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Describe "similar". You should set your ohm meter at 20k and your sensors should not be more than a few hundred ohms apart.

Does the error come up immediately or after running for a bit? Is the pump that circulates water through the heater working, and moving water? Remove filter and reset breaker.

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Given this is a Balboa board, "Sn" is sensor sync (as opposed to say Sa or Sb where sensor connection is faulty or disconnected). Your resistance values are not agreeing with eachother, if your multimeter has good accuracy you should probably be able to diagnose this yourself, like RDsapguy says, they have to be within a few hundred ohms. 

The balboa VS spa packs have 2 sensors one inlet one outlet on the heater and no hi-limit. 

*Edit* also the "Sn" usually comes up at lower temps where the ohms change more per degree than at higher temps. So for me when I had bad resistance values it would only trigger when the spa was 100 degree or lower and it would be fine so long as it stayed hot like 103, 104.

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  • 2 weeks later...

I lost this forum! Somehow the emails were being sent to my spam! I got that fixed and found you guys again! Thank you so much! Ya'll really seem to know what you're talking about!


I get the code about 45 seconds after I turn on my hot tub, which I do by just fliping the breaker on.

I took another reading (water hasn't been heated, not sure on water temp but ambient temp is 54F).


On my multi-meter the probe before the heater is reading 47.90 the probe after is reading 56.36. Last time they we're both at 42 and just off by .44

My meter doesn't have different resistance settings, after the numbers it does say k, then the ohms. 

But maybe now this shows that maybe one of them is actually bad. Visually they look perfectly fine, but I don't really know what to look for.



You guys are awesome and thank you so very much for the help! This place is great!

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You should have the temp set below the current water temperature (i.e. not heating), and have the pump running for a minute or two. Then cut power and test the resistance values. This will ensure there was good flow through the heater and one side is not hotter than the other. Provided you do this - your ohms should be very close, within .1 on your meter (even .44 is too far apart, that's almost 2 degrees).

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