Mikes

@RDspaguy I thought that these were not the correct terminals to check the voltage.....I was following the video and this is where he measured.....but....all is good. I removed the Heater Relay Board and this is what it looked like. Burnt Relay. Replaced the board with the 4th generation board and the Hot Tub heats fine!

@RDspaguy @TheWGP Hi Guys! Remember me?? I "gifted" my hot tub to my brother in law. After the move (it was tipped on it's side - but done by a mover)......the tub no longer heats. I found a video on youtube where the person had a similar spa and determined it was the heater relay board. I viewed the video and at 4:10 in the video (Fixing A Cold Hot Tub... - YouTube) he describes how he measured the voltage on the old board. I did this and had the same symptoms as me. I ordered a new board (Caldera Spa Heater Relay Board 2002 - 2009 #77119 - Caldera Spa Parts Plus). Attached is a screen shot of the board and I circled where I measured zero voltage accross the terminals circled in red. Do you guys think I'm on the right track? Thanks in advance for your help!

@RDspaguy @TheWGP Well....High limit temperature sensor came today. That had to be the easiest thing in the world to replace! Held onto a groove on the heater with nothing but a fairly stiff foam insulation and two tie wraps on each end of the insulation. Anyway.....no dice. It was worth a shot! Still have the dancing display for the actual temperature. If nothing else, I learned a lot about the workings of the hot tub. I have the part numbers for the new circuit board and topside.....when/if it craps out I'll evaluate then if it's worth replacement. I've looked long and hard at the circuit board and wiring....and it looks like a replacement job that I can handle with no problem. Also while I was in there....I noticed that the neoprene tubing for the Monarch Ozonator was very "soft" in places....so I replaced that also. For now....I'll keep the temperatures far apart! Thanks for your help and input guys! Mike

If you don't care about the ability to monitor the spa temperature via the Internet.....then you don't need the Ethernet Hub.....there is a cheaper solution: https://www.acurite.com/shop-all/weather-instruments/weather-sensors-and-parts/displays/indoor-outdoor-home-environment-display-with-4-zone-capability.html Also....just ordered that sensor this morning and they shipped it out already!! Should get it maybe Thursday.

@TheWGP Keep an eye out on that web site for sales. They sometimes bundle sensors and the Ethernet Hub together at a pretty good savings. One thing I learned.....use name brand batteries (Duracell) for the sensors that are in "normal" temperature extremes......and if you are monitoring a freezer use Lithium batteries. I change them once per year. Also use https://wyze.com/wyze-cam.html cameras all over inside and outside the house to monitor remotely. So I have another question.....I didn't really pay attention to the high limit temperature sensor when I was replacing the actual temperature sensor yesterday. Can't really find instructions on how to change it. Is this surface mounted on the heater or am I going to have to drain down the hot tub again?

@TheWGP The temperature sensors I use are totally reliable.....I leave my home for four months during the winter and never have had a glitch. Here's a Link to the web site: https://www.acurite.com/shop-all/weather-instruments/weather-sensors-and-parts/monitor-with-liquid-soil-temperature-sensor-00275ls.html You also need the Acurite Hub to monitor it remotely on the Internet: Here's a link to the Hub: https://www.acurite.com/shop-all/weather-instruments/weather-sensors-and-parts/displays/access-my-acurite-remote-monitoring.html I have a complete weather (wind/rain/humidity) station also that is part of the overall system, and also probes for my refrigerator and freezer and basement, living room, bedroom, etc. I've attached photos of how I set it up the liquid/soil sensor in the Hot Tub, and also some of the other sensors I have (weather station and sensor in my freezer), photo of the Ethernet internet hub, as well as screen shot of how the Internet display dashboard looks. I live in upstate New York...so probably close to the same weather you get.

@RDspaguy and @TheWGP Thank you guys for your thoughtful responses. I really appreciate the time you are spending (virtually) with me and my problem here. I hear you about the "techs" from the OEM.....she did put me on hold for about 15 minutes and said she consulted with a senior tech.....but like you said @RDspaguy........ I have the High Limit sensor on order.....we will see if this solves the issue. It really isn't that big of a deal to keep those temperatures far apart.....especially this time of the year and summer. I even have a secondary sensor in the hot tub where I can remotely monitor the temperature on the internet. Got several because when we go away for the winter I can monitor the tub remotely, also freezer/fridge and room temperatures for any problems. Decided since though that it would be safer to winterize the hot tub in case something failed while away for the winter.....and also because of this fluctuation problem. One question @TheWGP....why are you hunting around for a new topside? What sort of issue(s) are you having....that I can look forward to?

Not sure @RDspaguy....high limit sensor or display and board replacement? I found a phone number to Caldera/Watkins Tech support.....they told me that the top end display needs to be replaced and they no longer make that unit so I would need to replace the control box also. They gave me the attached part numbers. The price seems high to resurrect a 20 year old hot tub! Might need to just keep the temp setting and the actual water temperature far apart until death do us part?

@TheWGP and @RDspaguy The actual temperature sensor came today. I powered down and drained the tub to below the sensor. Made sure I got the old intact O-Ring from the old sensor. Installed the new sensor and refilled the tub. Powered it back up and THE SAME PROBLEM STILL EXISTS!!! I know that @RDspaguy said to replace the sensors in pairs.....but I guess I didn't think the high limit sensor would affect the display of the actual temperature. Is it possible that the High Limit Temperature sensor can affect the display of the actual temp? If so, I can give that a try; buy a new high limit sensor and replace it. One thing I did try was that I powered the tub down again and disconnected the high limit temp. sensor and then powered it back up to see what would happen. What happened was I got a bar across the display screen.....powered the tub back down; reconnected the high limit temp sensor to the circuit board, powered back up and back to square one. So what do you think guys....do I replace the high limit temp. sensor also or do I call it quits and resign myself that it is the control board causing this problem??? I can always keep the actual temperature setting and the water temperature far apart......it bit of a nuisance but not too bad. I winterize the tub because I am not home during those months....so no worries there when the temps would be close together most of the time. Looking forward to your replies..... Mike

Thanks for those links @TheWGP . I ended up ordering this: https://www.spapartsdepot.com/caldera-spas-thermistor-control-for-advent-control-system-caldera-2002-to-current-72493/ I did see the calderaspapartsplus.com site.....but decided on the above because there was a difference of about $5.00 in shipping and no sales tax. So a bit less money. I have been thinking about that O-ring!!! I tried to find one on the site I used but the only thing they had was the entire assembly to house the sensor for about $20. I'll check out Lowe's if the one I have looks like it needs to be replaced. The dealer in our area told me that Caldera has been closed down throughout this entire Covid-19 mess....and they are running out of hot tubs to sell.....also having problems getting parts. He told me he could order me the OEM part.....but said it would probably be several weeks to get it. Also told me that he can't get a lot of the parts and has several customers waiting for replacement covers/etc. that he can't get because of the shutdown! This forum is awesome!! How else could you ever find out other people's issues with the same hot tub! I'll post again if this sensor repairs the issue I'm having. Thank Again!

@TheWGP Please ignore the above request for the part number. It is 72493. I was able to get through to a dealer! Thanks.

@TheWGP Could I pester you for the part number of the Actual Temp Thermistor? I have been searching around the internet and finding two different numbers 71578 and 72493. I noticed in your posts you have replaced that part in the past. TYIA!

Yes I did disconnect them from the board to test them. Also powered down the hot tub before testing. Which sensors should I replace? Do you have a recommended place to buy them? Thanks again for your help.

Yes I did disconnect them from the board to test them. Which sensors should I replace? Do you have a recommended place to buy them? Thanks again for your help.

Sorry about that! Quoted the wrong guy!! Thanks @RDspaguy

OK....hope I did this right. I posted pictures of my readings with the Multimeter. Working from left to right on the circuit board: Pressure Switch: Reads ".7" with meter set at 200 Ohm. no fluctuation in reading Limtherm: Reads " 6.45" with meter set at 20K Ohm. Fluctuates to 6.46 Regtherm: Reads ""6.8" with meter set at 20K ohm. Fluctuates to 6.81 \ Pictures posted below.....Thank You for the help TheWGP.

There was a board replaced maybe 16 years ago under warranty. I don't have a receipt for whatever reason......but I do remember it was to correct a problem with the clean cycle. The delay between the time the blower shut off and when the main pump went on was too short and caused something to trip out where I would get "Bars" across the display. Not sure but I thought it was the main board. Other than that.....no problems! (knock on wood). Also....I have been "Babying" this thing ever since this here problem arose with the "fluctuating actual temperature". Rather than let that relay/heater keep turning off and on continuously because of the fluctuation in the actual temp reading.....I turn the temp up to 102 degrees, let it get to temp, then turn it down to 80 degrees when not in use. I keep the actual temperature and the set temperature far apart so that the fluctuating actual temperature (jumps around two to three degrees) doesn't keep kicking the heater on and off continuously.

Not to sound stupid...but.....I just pull the connectors off the circuit board (after shutting down power). Then using the multimeter check the resistance on each of the connectors....one probe of the multimeter in each side of the connector? Never used a multimeter before. 18 years and never a problem with this hot tub!

I don't have a Multimeter.....but plan on picking one up tomorrow. I took the cover off though to take a few photos of the circuit board. I did notice some of the insulation on the left side white wire with yellow jacket looks burnt near the connector. I took a close up of that. I did unplug that wire and plugged it back in and it seems secure and the insulation around the connector is intact.

All is good with water flow through the circ pump. Good bubble flow from the Ozone generator as well. The unit was winterized....and this problem began last summer. I filled with fresh water and a brand new filter a couple of weeks ago. I don't have a multi-meter but I could get one if you can give me some guidance as to how to check the heat sensor.

It is the actual temperature reading.....

Help! I'm having the same problem. 2002 Caldera Martinique. Temperature setting "dancing around" and causing clicking of relay when trying to maintain temperature. My workaraound has been to heat the tub up to 102 degrees then turn down the set temperature to 80 degrees.....wait a few days and repeat! Is this repair my only hope? Any idea how much a dealer would charge to do this? Thank You.

I am having the exact same problem with my Martinique (2002). What did you end up doing?