StevenD Posted March 11, 2021 Report Share Posted March 11, 2021 Hot Springs/Watkins Solana TX. Can anyone tell me if I'm on the right track. The thermistor is part number 72493, if that makes a difference. Best I can find is at 104 degrees the resistance should be somewhere between 5-6 ohms. Yes/no? Is the a more specific reading? Temp difference has gone from 2 degrees to 4 now. Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted March 11, 2021 Report Share Posted March 11, 2021 https://www.backyardplus.com/proddetail.php?prod=38416 Scroll down to the testing procedure and you will find a chart. When testing for thermistor issues it is far more important that both be the same than that they be accurate. Your spa won't know if both are off by a degree or two, but if one is higher than the other it will cause errors. Test both and post results. If they are more than a few hundred ohms apart it will cause errors. I recommend replacing both thermistors at the same time. Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted March 11, 2021 Report Share Posted March 11, 2021 20 minutes ago, StevenD said: Best I can find is at 104 degrees the resistance should be somewhere between 5-6 ohms. Where on earth did you hear THAT? Thermistors operate in thousands of ohms. 5 ohms would be a mouse chewed shorted wire. 5k ohms (5000) is in the ballpark for 104*. Quote Link to comment Share on other sites More sharing options...
StevenD Posted March 11, 2021 Author Report Share Posted March 11, 2021 Thanks. Yeah that's the chart I was looking at. Will be checking both. I know there's a 2 degree give/take between actual water temp and what the control panel uses to turn on the heater so wasn't too concerned at first. But now set at 104 water temp is only 100. Checked several times throughout the day and evening. Quote Link to comment Share on other sites More sharing options...
StevenD Posted March 11, 2021 Author Report Share Posted March 11, 2021 10 minutes ago, RDspaguy said: Where on earth did you hear THAT? Thermistors operate in thousands of ohms. 5 ohms would be a mouse chewed shorted wire. 5k ohms (5000) is in the ballpark for 104*. Typing too quick. Yes 5000 Quote Link to comment Share on other sites More sharing options...
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