hottubtimemachine Posted September 8, 2023 Report Share Posted September 8, 2023 I need some help, as I am trying to fix my dad's hot tub for him. I've already scoured the internet and I'm stumped. Background: It is a 2007 Sundance Optima. A while back, he went out to the tub and found that the water was luke warm. There was a FLO error on the screen. He asked me to fix it. I was able to see that the circulation pump motor was not spinning, but had power to the terminals. I got it spinning with a pair of pliers as it was seized up. I then replaced the motor with a new motor/pump unit and now it's pumping water perfectly! Current Issue: Almost immediately after fixing that, there is another issue that is very hard to diagnose. The water temperature reading is not accurate, and fluctuates between about 1 and 17 degrees higher than the actual water temperature. First thing I did was check resistance on the two temperature sensors and both are correct. At a water temperature of 100, I measured a rock solid 17.4kOhm and 17.6kOhm on each sensor. I also checked at a lower temperature and it correlated correctly. The power was off to the spa during my diagnostics. When I powered it back on, the temperature was now reading accurately for about 1 day. I went to check it the following evening and it was still good. I then checked it about an hour later as I wanted to test it out, and it had risen to 110F even though the water was only 100F. The set point is 104. I decided to check the resistance again and it was all good still. When I powered on the tub again, it now measured correctly again! But... as I stood there watching it for 3-4 minutes it began to rise to as high at 118F, and displayed a flashing OH error. I then could hear the circulation pump and heater turn on and off as the temperature fluctuated between 101 and 118 sporadically. So... even though the temperature sensors are the most common and cheapest failure, I don't see why I should replace them if they are measuring accurately. There is one other issue that might be related: The buttons on the topside display are doing weird things - such as when I press the left jet button, the right jet will go on instead. There is some cross-talk going on there. The temperature setting buttons seem to work fine. I have a feeling it's related to the circuit that decides what to do with the temp sensor resistance. Either a voltage is off, or there's a short/open circuit somewhere. Either that or the temp sensors Ohm out fine, but when connected to the actual circuit it goes haywire. Any suggestions on diagnosis before I start throwing very expensive parts at it? Thank you Quote Link to comment Share on other sites More sharing options...
CanadianSpaTech Posted September 8, 2023 Report Share Posted September 8, 2023 6 hours ago, hottubtimemachine said: it began to rise to as high at 118F, and displayed a flashing OH error. Temp sensor is my guess. See this often with Jacuzzi products. Was the sensor replaced recently like within that past few years. There is a recall on Jacuzzi temp sensor. Not sure if the recall effects only those installed in new spas or if they were shipping out the bad sensors for the repair market as well https://recalls-rappels.canada.ca/en/alert-recall/sundance-spas-and-jacuzzi-hot-tubs-recalled-due-burn-hazard Quote Link to comment Share on other sites More sharing options...
hottubtimemachine Posted September 8, 2023 Author Report Share Posted September 8, 2023 3 hours ago, CanadianSpaTech said: Temp sensor is my guess. See this often with Jacuzzi products. Was the sensor replaced recently like within that past few years. There is a recall on Jacuzzi temp sensor. Not sure if the recall effects only those installed in new spas or if they were shipping out the bad sensors for the repair market as well https://recalls-rappels.canada.ca/en/alert-recall/sundance-spas-and-jacuzzi-hot-tubs-recalled-due-burn-hazard The temp sensor is original to the spa. It's the all plastic light grey colored one. Is there any more testing I can do to confirm it's the sensor, perhaps while it's installed? If the resistance is right and it is reading the wrong temp, then maybe it's a power supply issue? General question... does the topside display interpret the resistance or is that done on the control board which then sends a signal to the topside about which digits to display? Quote Link to comment Share on other sites More sharing options...
CanadianSpaTech Posted September 8, 2023 Report Share Posted September 8, 2023 5 hours ago, hottubtimemachine said: done on the control board When ordering make sure you know what connectors you have... either box ends or Curled finger ends... https://www.hottuboutpost.com/sundance-spa-box-end-temperature-sensor-6600-167/ https://www.hottuboutpost.com/sundance-spa-curled-finger-temperature-sensor-sun6600-166/ Quote Link to comment Share on other sites More sharing options...
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