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Jacuzzi J365 watchdog "----" error


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You could have a few different problems being masked by the watchdog error.

The circulation pump not running would not cause the watchdog error by itself. 

If the circulation pump is not running, and the flow switch is bad, the heater may turn on without any water going through it.  This would cause the hi limit to activate the watchdog error. 


To test if the circulation pump is working, you would have to test when the watchdog error is not present.  If it is not running, the flow switch is open, and the heater comes on, you would have the scenario I posted above.

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When that system starts up the first thing to turn on is the circulation pump. It moves water through the heater and closes the flow switch. Once it has detected flow and the switch has told the circuit board there is flow it the allows the heater to turn on. If the flow switch is faulty or the circ pump is not flowing water then it should not turn the heater on. Now if the circ pump is working intermittently which is not uncommon with the small Laing circ pumps it might detect the flow and turn on the heater but then the circ stops working and now the heater still has heat in it and normally after a heat cycle it takes up to 30 seconds to cool the heater (when heater on with no flow it will boil any water in it in 1 second...or less) it will detect that residual heat and send a hi limit error and then a watchdog error after several tries. The circ stopping mid heat cycle doesn't allow the heater to cool and the hi limit hits right away. If you look at the flow switch on start up you should be able to see into it and watch what happens. If the clear housing of the flow switch is yellowed and hard to see into hold a light behind it so you can see if the circ is starting and stopping and closing the toggle against the post and then pulling away from the post when the circ stops. You might be able to see this starting and stopping by watching the waterfall as well. The circ might run for 10 seconds or it might run for 5 mins then stop and start again...or not.. again intermittently making it hard to diagnose. This is ONE possibility. 

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Hi all, thanks for your replies.

To clarify, upon powering up spa goes to watchdog mode in less than a second.
While turning on the breaker I watched the flow switch , it is not moving (stays open, before, during and after resetting the breaker). Pf course, no water fall.  I also touched the heater, it is cold all the time.  Circulation pump is not vibrating or otherwise making any noise at any point (I doubt the pump is working even intermittently).
As CanadianSpaTech mentioned, it appears to me that circulation pump is not turning on hence there is no flow + the heater never comes on.

Do you have any feedback on what to do next?
I am not familiar with using a multimeter (but can follow directions :)
(I did figure out how to check for continuity of the fuses in the box, they checked ok)

I am leaning towards ordering the circulation pump (although I'm not sure the existing one is dead and don't know how to test it) but will wait for last minute feedback from the experts, thanks!



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