Miniondx

Thanks for the insight, I will look into those things. My issue is, though, if I unplug the control panel (the topside panel with buttons for jets, temp, etc) it will run forever on low speed and never surge. Is that normal? Or an indication of a bad control panel? Also, while replacing the old heating element, I noticed the heating assembly tube didn't exactly span the entire distance from one connection to the other, it never leaked before so I'm not sure how they managed that, but I had to create some new seals with silicone gasket maker + epoxy. It seemed like it worked since there were no water leaks, but could it be possible that's where it is sucking air, since the heating assembly is on the "in" side of the pump? Is a small pinhole leak enough to cause the surging? The action of the pump kicking on high speed and off creates a lot of vibration in the pipes as well, possibly causing the problem to sustain itself as those seals get compromised. Thanks for the info, it's nice to have a few more leads to check before diving in on the $250 panel, only to find it has no effect. I guess there's no such thing as a "free hot tub." Lol

Okay, I got it working finally. There was an auxiliary control panel on the other side of the tub, so that a person sitting in the "main chair" could turn the jets on and off without having to get up I suppose. The two cables from the main panel and the aux panel were spliced together, and plugged into a single input on the circuit board. I had a eureka moment when I saw that and figured the two cables must have the same function to be plugged into the same input. I separated the splice and attached the connector onto just the main panel side of the cable, and plugged it in. Success! Everything is functional: the jets, lights, temp, and panel. So I suppose there was some sort of short in that aux panel that would cycle the jets on and off repeatedly. EDIT - SCRATCH ALL THAT. It ran for a solid 8 hours before doing it again. My temp gun would read 108F when it was surging, I cut the power and the still water reads 88F. Maybe it is overheating in some way? Perhaps this is a sensor issue? Clogged pipes not circulating the heated water thoroughly? At least I have a few things more to check, but I'm taking a break from it for a bit.

I got a free hot tub from my neighbor who was throwing it away. It was tripping the GFCI on power up consistently. I narrowed the problem down to the heating element. Replacing it fixed the tripping, and I needed to replace the transformer and pressure switch to get it to heat. So I turned it on and watched it for a bit, looking for any leaks. When everything looked fine and operational, I closed everything up and turned it back on for the night. I made sure I could turn the jets on and off, the lights, and set the temp to 100F. Next morning everything was fine, the hot tub was at 100F and idle. I was watching it when the filter cycle came back on, considering getting in, when the pump starts sporadically coming on and off. It's a two speed pump and I mean the high speed (jet speed) would kick on for a second, then shut off and repeat that infinitely. The control panel was unresponsive. I watched the inside of the box while this was happening and the relays would kick on in series 1-2-then click off. Over and over. There was minor sparking and arcing at the magnets while this was happening, but I think that is part of normal relay operation. I thought maybe the condensation from the cold water heating up in the pipes maybe got on some of the controls, or the humidity rose to the underside of the panel or something, so I shut everything down. A couple of hours later everything was working normally again. This lead me to believe it was moisture related. So I made sure everything was functioning normally, and started to cover the complete underside of the panel with dielectric silicone, and while I was at it, redid the seals on the top side as well. I wrapped the cords that plug from the panel to the circuit board with a shop towel and put some more silicone around the socket. I am pretty confident there's no water getting into the control panel or where it plugs in now. But the problem persists. If I unplug the control panel everything works fine for hours on end, but there's no way to turn on the jets or change the temp. Plug it in and I get the surging. I really don't want to replace a $250+ panel, I already put $100 into the tub, I could of probably converted the whole thing to pneumatic at that rate, so if anybody can give me a fix or workaround I'd be really grateful. Its a Marquis "Leisure Series" panel, with a Balboa LZR1U circuit board. I should add that letting the hot tub run with the control panel unplugged (so not even resting) for an hour or two, then plugging the panel back in will work everytime, for about a minute before the problem returns. I can adjust the temp and turn the jets on and off during this grace period. I've tested the water temp with an infrared gun and the panel is displaying the temp accurately and there are no messages.