Sundance 2000 Cameo 850 series Heater won't shut off



I've used another forum in the past, but my problem was never resolved. Doing some 'Googling' and ran across TFP which looks promising. I'm an excellent DIY and have a degree in electronics engineering, so I know my way around a SPA. Here's my problem. My 2000 Sundance Cameo 850 series with the 'Controller 850LCD' circuit board seems to not want to shut the heater off until I get the hi-limit sensor error of "OH" on the display. I have a free floating thermometer in the water which corresponds to the display temperature at all times. Here's the scenario: I can set the temp on the top control panel to 102 F. If the water is several degrees lower than that, the heater will run up to the OH error which is around 108 on my tub, shows 108 on the display panel, shows 108 on my free floating thermometer, and feels like 108 to the touch.

KEY NOTE: The 'heater icon' on the display does show until the 102 mark, but goes off above that, but I can still measure voltage across the heater terminals. Here's what I've done:
  1. Tested the hi-limit and temp sensors with an ohm meter while in the tub and also after bringing them into the house. The resistance matched what the tech charts said they should.
  2. Had an extra hi-limit and temp sensor from an issue I had years back with a heater meltdown. They tested fine and I even tried those in the SPA in place of the above ones I had already checked. Nothing changed. Heater still runs to the "OH" error.
  3. Replaced the circ pump in case I had a low flow problem resulting in higher than normal temps in the heater. Old one was getting old anyway, so what the heck.
  4. Tested the flow switch with an ohm meter while water was flowing through it and while power was shut off. Opened/Closed as it should be. Good. I have never had any "FLO" error messages.
  5. I pulled the motherboard and tested for shorts across the main leads on all relays. Also applied a small DC voltage, using a 9v battery, to the coil terminals on all relays and could audibly hear them opening and closing (though one for the circ pump sounded a little loose). I couldn't find a schematic for the board, so I had to visually follow the trace lines on the board. That was fun.
  6. Visually, the board looks good. Can't see any burn marks, blown caps, etc....
  7. I can run the SPA normally with the heater disconnected. All functions seem to work fine. 2-spd motor, 1-spd motor, circ pump. I don't have an ozonator or blower anymore as those gave out years back and I never replaced them. I believe in simplifying.
  8. With the heater connected, and it heating up so high, I have occasionally tripped the GFCI breaker. I'm going to test the resistance on the heater element in a little bit.
I'm at my wits end. For now, I'm going to put the board back in, try the heater to see what happens but will more than likely disconnect it again. I may try leaving all 3 sensors disconnected along with the heater, to see what error messages I get on the display and then hook up one sensor at a time, just as a verification that the logic and sensors are working correctly. I think I will go ahead and order a new hi-limit and temp sensor, since that isn't too much money. I hate the thought of buying a $500 circuit board.

Any ideas? Would really appreciate it.


New info. I placed the circuit board back into the cabinet. I hooked up the pump1, pump2, and the circ pump. I purposely left the sensor switch (temp, hi-lo limit, flow switch) and heater disconnected. I turned on the power and got a S1 - S3 error. Made sense with the sensor harness disconnected. Had no voltage across the heater leads.

I hooked the sensor harness back to the board, but took out the Flow switch tines. Turned power back on. S1 and S3 no longer show. But, I get a "FLO" error as I should with the flow switch disconnected. Now the interesting part. I still measured 240vac across the heater terminals even with the Flow switch disconnected and getting a "FLO" error. I'm really thinking the circuit board is shot. It is 20 years old after all. Also, the measured resistance across the heater leads is 10.6 ohms. That's within spec.
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I played around some more and I am pretty certain some of the relays are bad, even though they tested okay on the bench. The display works as it should. I increase the set temp and I see the heater icon come on, I decrease it and the icon goes off. I set the board to 50A setting (removed jumper 7 on JP9) so that when I have both pump1 and pum2 running on high speed the heater can't run. I tested this by setting the set temp real high so the heater icon kicked on, then turned both pumps on and the heater icon went off. So I believe the 'logic' of the board is working okay. After setting the set temp way down below the actual temp, I was still measuring 240vac across the heater terminals when I took a screw driver and tapped the 3 big relays that control the heater. It went down to 1vac and stayed there. Set the set temp higher and got 240vac to the heater. Set the set temp back down and still got 240vac until I tapped the relays again. Looks like a sticky relays that doesn't switch off after switching on. So I do believe the relays are bad. I do appreciate any thoughts from anyone whose had to delve this far into troubleshooting a hot tub before. Thanks.


If anyone is interested, although all I hear is crickets from this forum, I replaced the 3 main relays for the heater and all is well. Pulling the circuit board and removing the old pieces and soldering on the 3 new ones took around 2 hours.


New member
Nov 3, 2021
Plain City
Hello Nessundo it sounds like the exact same spa (Cameo with 850 controller) and-problem I have. I notice the heat stays on even when the on the control screen it says the heat is not on. I will kill the power and things reset for a day and then go back to OH. I am assuming that a relay is bad. Can u explain where the relays where that you replaced? I am not a electrician, but I can solder and do about anything. Im considering just replacing the entire board. Any assistance would be great. Would really like to give you a call if possible to talk thru this. Thanks for the great post!
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Well-known member
Feb 17, 2021
Wentworth, NC
Need to see exactly what you have. Post up any wiring diagrams on the cover and a picture of the Spa Pack PCB. Most have larger Zettler relays near the heater contacts.

The hard part of the repair is pulling the board and labeling all the connections. Replacing the relay's is using some solder wick and patience.
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