I recently got a used hot tub and I am having problems with it over heating regardless of what temperature is set. I set the temp to 90 degrees and the tub climbed to 112 degrees and HILI appeared on the display. The Heater icon seems to display correctly at times when it needs to be heating (at or below the set temp). Once it reaches the set temperature, you can hear a relay click and the jets shut down (except for the auxiliary pump that runs 24/7) and the heater icon goes away. Come back a few hours later and the temp has continued to climb. I have to shut the breaker off in order to get the water temp down.
I've done some electrical testing.
Wiring diagram:
https://www.dropbox.com/s/07h3g3djujr9yew/IMG_5971.JPG?dl=0Labeled photo:
https://www.dropbox.com/s/rif01l8jytofgln/hottub.JPG?dl=0On the labeled photo, I marked A-Ground, B-Heater 1, and C-Heater 2. When the water temperature is above the set temperature, I measure VAC with my probes on B and C. I get O volts. I had my wife begin to move the set temperature up above the water temperature and you hear the relay click, jets kick on, and heater icon turn on. The reading jumps to 240V. Seems right to me so far.
Next, with the wires unscrewed from the board at B and C and the set temperature below the water temperature, I placed my probes on A and B and I get a OV reading. Move the set temperature up and cause the relay to click, jets kick on and heater icon turns on. The reading at A and B now reads 120V. Seems right again
Do the same at A and C. I am getting 120V regardless of set temperature above or below the water temperature. Am i right to think that the relay is stuck on and this is where the heater continues to get some power to heat even once the icon and jets are off?