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Sundance Altamar watchdog error

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I have a 2000+ Sundance Altamar spa giving the 'watchdog' error (---). I have gained a lot of insight on the forum but I am a little confused by my troubleshooting thus far. With repeated power ups the display either shows the watchdog message, nothing, or random meaningless segments. I have no circulation, heater or pump action. If I video the LCD when the breaker is thrown I see a high temp - 102 to 108, then the error message. The only thing that makes a difference is if I unplug the sensor plug completely, then the LCD shows a variety of messages. If I remove each sensor (temp, overtemp, flow) the LCD always goes to the ---- message as long as the interlock jumper is in place.

Already done:

Power, 120/leg and 240 between the red and black

Transformer, ~14V and 10V (14 is a little out of spec)

Temperature and overtemp sensors, Ohm out to the correct temperatures when tested at bare connectors

Flow sensor, test shows it is working correctly

Circulation pump, works properly when jumped to power

All fuses checked out of system and are fine

Disconnecting heater doesn't change anything

Disconnecting one or both topsides doesn't change anything.

At this point I suspect either the temp sensor (due to the high reading on video) even though it tested to the appropriate resistance, or the 'capacitor problem' though I don't see how removing the interlock would make a difference if the board isn't getting correct power. Or is it just a bad board? The board looks fine.

My plan is to replace the temp sensor, if that doesn't work then pull the board and replace the caps.

If it's not either of these I am going to investigate an alternative control unit. The Sundance board is over $400 and nothing says that replacing it will fix the system. I would rather just replace the whole system with something like the United Spas C5 for low flow heaters. It is $500 but if I currently have some faulty component that damaged my board putting another board in just leaves me out $400. Replacing the whole control system including the heater seems like a good $100 bet. Does anyone have experience with doing this on a Sundance spa?


The problem was one of the big capacitors in the middle of the board. Replacing the caps is an easy job if you can use a soldering iron. Caps available on Amazon (not cheap, but easy) or Digikey. Swapping them out was a 45 minute cover off to cover on operation. The 'bulge' that some posts mention was very small in my case, the cap on the left in the image is bad.


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How exactly did you check the  fuses outside of the system? Fuses cannot merely be tested for continuity but, should be tested for voltage on the circuit board with power live. If you are getting anything but 0 voltage then you have a bad fuse. I can tell you right now that nothing is going to heat if your circulation pump is not running. The fact that it is not running is an immediate red flag to me. Since you have confirmed the circ pump to work, you need to figure out why it is not running. Your circ pump should turn on immediately. Are you getting power on the circuit board where your circ pump plugs in? Confirm whether or not you are getting voltage between the white and black on the circuit board where the circ pump connects. https://www.sundancespas.com/media/3414/850-series_english-2.pdf If this diagram on page 33 matches your circuit board, it would be at TB2. In my humble opinion, if you are not getting power to your circ pump from the board, and the pump is confirmed to work, then perhaps you have a bad capacitor on board. 


Ooops sorry. I just typed this all out, only to realize you had discovered the bad capacitor.

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