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I guess it's possible to learn to live with a spa which doesn't reliably hold temperature, but it would be We're living with the problem, but it's work. I've tested everything recommended to me and none of them seem to be in failure mode.

There are usually two motors and pumps. The smaller heater motor and pump usually runs constantly. The larger jet pump usually runs on command. jack vines

X2 - if the heater circulating pump is not running, it's dead or there's a serious control issue. However, you say "pumps". The Kauai only has two and the jet pump is NOT supposed to run all the time. jack vines

Greetings, We have a 2005 Caldera Kauai and enjoy it every night. One of the best features of the older models is the +1UT and +2UT functions. This means they can maintain 105 degrees or 106 degrees. We feel the difference and would not like to lose the ability to choose those temps. Having said this, we're having some issues with the unit holding constant temperature Sometimes it drifts down.. One suggestion was it may be a heater relay control board problem. We'd spend the money for a replacement in a minute, but are concerned any new control board may have the safety nazi 104 limit built in. Does anyone have any experience with this and can speak from experience? jack vines

These rolling, random problems are not fun to diagnose. For two days, it held at 105 degrees and then POOF,; it drifted down and for the first time ever, rebooting wouldn't get it heating again. I spent a day doing all the testing and troubleshooting without finding any definitely failed parts. Reassembled everything and POOF, the three days so far, it's holding 106 degrees. Dave, I'm going to ask for a favor to help me understand the control logic and what does/affects what. Please correct any misunderstandings I've gotten: 1. Turn on the spa. Temp is below set point. A low limit switch checks the pump pressure and if the pressure switch says OK, it starts the heater. 2. When the water temp gets to the set point, an upper limit switch turns off the heater. 3. Should the upper limit switch fail, there's a 115(?) degree over temp/safety switch. If this is triggered, does it always shut down the system and wait for a repair or reboot? 4. Since my temp never goes beyond 106, why does the control system sometimes shut down and require a reboot, but function as it should other times? 5. Even more confusing, once, when we were gone, I set the temp at 80 degrees, where there should have been no possibility of triggering the over-temp switch, and it failed to hold 80 degrees. 6. Now, rebooting doesn't trigger a normal sequence. New filter, heater circulating pump feels strong. Pressure switch is working. Am not getting 220v across the two heater terminals. Does this indicate a failed heater relay circuit board? If I jump 220v to the two heater terminals, would it begin to heat? Does the exterior of the stainless pipe begin to feel warm? 7. Should I just replace the pressure switch and the high limit switch as normal wear parts? Anything else while I'm in there? From whom would you recommend ordering Caldera/Hot Springs/Watkins parts? Thanks in advance. jack vines

Hi, Dave, Thanks for the suggestion and I'll order the part to have on hand as soon as the outside temps get conducive to lying on the ground. jack

Always a mistake to assume because two things happen at the same time that they are related. For a couple of weeks we had mild temps in the 40s and the spa would hold between 103-105 degrees. However, since the outside temperature has dropped into the single digits, the spa will no hold temperature at all. It loses a degree an hour until it is rebooted; then it immediately heats up to 105 within an hour or two. When the temperature reaches 105, the heater shuts off and will not restart without a reboot. What about colder outside temperature would prevent the heater from holding temperature? jack vines

One and then the other. Our hot water heater uses soft water, so fill half soft, half hard. Anyone see a problem with that? jack vines

As mentioned, an intermittent malfunction is frustrating. After holding near 105 for a couple of weeks, the temp drifted down to 98. A reboot brought it back to 105, but still no diagnosis. jack vines

I no nothing about the Coleman, other than the materials say they're outdoor rated, so why not use it outside in the winter? The one thing for certain, moving in and out semi-annually won't be good for longevity. jack vines

Wish I could help and hope you find the problem and the fix, as our Caldera is having a very similar problem. It wouldn't kick on to heat without an OFF/ON reboot and not always then. We were away for a week and turned it down to 80. Our daughter checked it and it only took one reboot to hold 80 for a week. When we returned home, I ran it up to UT1 and it's been holding 105 for two weeks now. It's difficult to understand why raising/lowering the set temp should make a difference, but as long as it's holding, we aren't touching that button. jack vines

When the problem comes and goes makes diagnosis difficult. We were gone for a week, lowered the setting and it held 80 degrees. We're back and now it's holding 105 (1UT) for a week. jack vines

Aha! So the pressure switch is adjustable? Thanks for that valuable info which I've not read anywhere in two weeks of searches and researches. The 1/8-turn should be in or out to reduce the sensitivity? jack vines

Thanks for the suggestions. I've been watching the temperature display several times a day. It seems accurate and it has never shown a temperature above the set point; this indicates the high limit isn't the problem. Yesterday, just to experiment, I tried the UT1 and sure enough saw 105 for an hour or so; then it stopped heating began to coast downward. After the football game, when we went in, the temp was down to 101. Manually pressing the "Set" button got the heater working again and a strong flow of hot water raised the temperature one degree while we were in it. If a function were completely failed, it would be easy to find. That everything works part of the time makes it more difficult. jack vines

Thanks; that's what I would have thought. I guess I was fortunate, as I drained and filled my Kauai and the jets and heater primed and produce full volume without any burping. jack vines

Hi, Dave, What are the symptoms with air in the jet pump? jack vines

We have a ten-year-old Caldera Kauai with a fluctuating temperature problem. It will usually heat up to 104 degrees, sometimes hold that for days. Then, randomly, it won't heat. Rebooting via shutting off power will usually get it heating again, sometimes not. Sometimes, it takes several reboots to get it to kick in. Now that the temperatures are below freezing, this behavior means we can't leave the place for any length of time without worrying it will freeze. All suggestions appreciated. 1. Plenty of continuous flow out of heater outlet in the bottom center and when the heater is on, output is definitely hot. 2. Timer for clean cycle works on schedule. 3. Never any error codes displayed. 4. Jets all have excellent flow. 5. New filter. As an experiment, I set it at UT1 and it reaches 105 and is at present staying there. How would varying the set temperature affect the sensor which cuts off at high/cuts in at low? jack vines