Michael SG Posted April 17, 2021 Report Share Posted April 17, 2021 Hi, any help is much appreciated. I have a 2010 Sundance 780 Series Hamilton spa that we inherited when we bought our house. It stopped working about a month ago and I've been troubleshooting it off and on and feel stumped. The issue started with the GFI being tripped. When I reset it, things appeared normal and then I started getting the "---" watchdog error. Everything I read online said this is usually a bad sensor. I replaced temp and high limit sensors and still got the watchdog error. Then the GFI started tripping again and I realized the heater was leaking a bit and badly corroded. So I just replaced the heater assuming that the corroded contacts were throwing funky voltages that set the board into watchdog mode. I'm still getting the watchdog error. It seemed random at first, but the more I've been troubleshooting I feel very confident (but not 100% sure b/c I've never actually been able to see the exact moment it goes to watchdog error) that the error is being thrown at the END of a heating cycle. The tub will heat as long as necessary depending on the starting temp and then error once it's done. So if the water is 95º and it's heating to 100º, it will heat fine for maybe 1-1.5 hours, all jets work, etc. until it gets to 100º and cycles off and then I get stuck in watchdog mode. OR if the water starts very cold like it just did when I refilled it thinking the heater issue would fix everything, it ran fine for several hours (7+ hours) heating the water from 51º all the way to 100º and only THEN did it throw the error. So it seems really closely associated with cycling the heater off. Does this suggest any other components for me to inspect/replace outside of the temp sensor, high limit sensor, and heater? Should I look at the 240 volt transformer? Or does the consistent error point (end of heating cycle) suggest I need a whole new board? Thanks! Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted April 18, 2021 Report Share Posted April 18, 2021 Does your spa have a 24 hour circulation pump or use the main pump to heat? Sounds like a stuck heater relay on the board to me. Do you have a voltmeter? Get it heating, then turn the set temp down below the actual temp while testing voltage to the heater, or wait for the pump to turn off and listen for a hissing or gurgling sound from the heater. 1 Quote Link to comment Share on other sites More sharing options...
Michael SG Posted April 18, 2021 Author Report Share Posted April 18, 2021 Thanks so much for the reply. This spa has a circ pump that seems to working (there is a waterfall feature which is a pretty clear indication that it's moving water). After reading another post here: https://www.poolspaforum.com/forum/index.php?/topic/49108-jacuzzi-j325-watchdog-error/ ...I was starting to come to the same conclusion as you - heater stuck on. Today it's behaving differently. Went out to add chemicals and it was on watchdog error. Reset it and it first started flashing OH then began acting "normally" - pumps working, etc. Temp display has always been correct...HOWEVER....I noticed today that I had it set to 98 and the spa was at 102 and the heater display light on the control board was still on. So this would suggest the stuck relay, yeah? I haven't opened it back up yet to check whether there is voltage to the heater, but I'm guess this is it. I then set the temp to 95 to see if it would at some point stop heating, but I watched the temp rise to 104 and then another watchdog error. 1) Any way to revive a stuck heater relay or does this mean it needs a whole new board? Side question, in that post I linked above it was explained you should be able to touch the heater and it would be hot but not scalding (<118º). I was going to check the surface temp of the heater but it felt VERY hot to me last I was poking around in there. 2) Would surface temp of the heater over 118º indicate the circ pump need to be replaced too even though it is still moving enough water to to activate the flow switch? I've read circ pumps sort of either work or they don't, they don't "slow down" ... so if it's still moving water should I wait to replace it? THANK YOU! Quote Link to comment Share on other sites More sharing options...
Michael SG Posted April 18, 2021 Author Report Share Posted April 18, 2021 Confirmed it's a stuck relay. Went out there and watchdog error was displayed. Heater was gurgling and had voltage. Surface temp of heater was 125º with no water flowing. I am assuming the heater relay is K8, but not sure which. I tapped them all and nothing tripped/flipped. I could probably start by replacing the relay before I replace the whole board? Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted April 19, 2021 Report Share Posted April 19, 2021 K7 and K8 are for the heater. An electronics repair shop should be able to replace them pretty cheap. 1 Quote Link to comment Share on other sites More sharing options...
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