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spa bubbler comes on inappropriately


beg
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Hey all.  Looking for some direction to fix my hot tub problem .  I have a 20 year old tub with a Spa Builders LX -15 spa pack (revision 7.51 sticker on the EPROM).   The motor and pressure switch have been replaced; but I believe temp sensors are from the original build.

When heating the spa and the temp reaches 97 degree; the bubbler ( to cool the water) comes on.  The heater stays on and there are no error codes generated.  This will keep happening  several times (after turning off the bubbler) ; until the water is at 97 or 98, and then it typically won't happen again.  Also, in a possible related issue; the water won't heat to 104.  The bubblers come on, the heater turns off and I get an OH code at cooler and cooler  temps (down to 99 degrees) (this problem appears progressively worsening in that, over time, the spa is reading OH at cooler and cooler temps). 

I have checked the water and hi temp sensor; they both read similar ohms and appear to have the correct resistance (per the spa builders trouble shooting guide) and the water temp of the spa on the top side correlates with a thermometer in the water.

Otherwise the spa works well with no other error codes.  The ozonator with the spa no longer works dating back years ago.

I''m thinking I need to replace the circuit board; it just seems like an odd way for the logic system to fail.    Thanks for any insight.  Circuit board and circuit diagram pictures attached.

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IMG_1397.JPG

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Remove filter. Check water flow. 

The behavior you describe is most likely a flow restriction causing the heater to get gradually hotter, as the flow is not enough to keep up with the heat produced and overheats the heater itself but not the spa. 

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Disconnect the blower and see if it heats up to set temp. Take it out of the equation.

Make sure the temp probe is all the way in place. If the probe goes through the side wall of the spa and physically touches the water then it is all the way in. If the probe goes inside a tube and doesn't actually touch the water make sure it is pushed all the way in so it touches the front of the tube so it can read the water temp. If it's not all the way in it won't read water temp correctly. It should also have a plug or cover of some sort once it is all the way in so cold air does nor reach the back of the probe.

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thanks for the replies.

I will try those maneuvers and repost.

The water temp sensor is in a thru wall thermowell.  I'll check it.

I did replace the filter recently without any change in the blower turning on.  Not sure if there is another way to check for flow restriction.

I also tried to address the problem by running the pump on hi while heating the  tub; without fixing the issue.

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The blower will turn on from an overheat in an attempt to cool the water. This will show the "OH" overheat error. This error is triggered by high temp reading at the high limit sensor that should be on the heater. Low flow is the main cause of this, and filters are the main cause of that. 

23 hours ago, beg said:

also tried to address the problem by running the pump on hi while heating the  tub; without fixing the issue.

This may disable the heater, but should not cause the blower to turn on or cause any OH error. If the OH occurs with the jets on high, and all the jets have good flow/pressure, it is not a flow issue. Check jet pressure.

Otherwise, I'd replace the sensors.

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