Tubcat

The 'solution' is to check often, especially during cold winters, and turn off and on when the dashes appear. The only option I have now is to get a new motherboard, which I haven't bothered doing. Turning off and on has worked for three years now, so I've accepted that for now. The tub is 2008/2009, so I'm done putting money into it.

Nope, but I believe I have exhausted everything but the actual main board at this point. I've done the following, (a recap of the above posts): - new filter - new high limit sensor - new circulation pump - checked the heater relay board for obvious signs of any issues - bypassed the pressure sensor as I didn't want to replace something that didn't need replacing. There are also no trees in the backyard or near me, so the water has never had leaves or any other sort of debris in it, and we enter the tub from a deck. So all signs point to main board issue. Everything works great otherwise, but every 3 weeks or so I have to turn power off and back on to resolve the heater being shut off and the 3 dashes on the display. Doing this has always resolved the issue over the last 3 years. The only frustration is that I'm in the North, so during the cold Winter months I have to check every day that the heater is still running and present the tub from freezing.

I have replaced the: filter (they were always clean, but got a brand-new one and a back up which is relatively new), high limit sensor, circulation pump (the older one was noisier and 10 years old, so I figured the new one was going to be needed soon anyway). The trombone heater look like the following, and the pressure switch/sensor is in the black casing. I just wasn't sure how easy it was to replace as all the pressure switch examples I've seen are visible when the tub is opened up:

Replaced the circulation pump and the problem still occurred. The latest thing I am checking is whether it is the pressure switch. This is in a Low Flow Trombone Heater, but for now, after spending time on every other solution, I have simply bypassed the sensor on the circuit board with alligator clips and will see if I get the same error. 5 days so far with no problems, but the error can sometimes take a few weeks to occur. Anyone replaced a pressure sensor in a Low Flow Trombone Heater?

Before I go forward with an expensive support call, I wanted to see if anyone else may know what is going on with my tub. The heater works fine, but randomly every couple of weeks, I will get the dashes on the display indicating hi limit tripped, and the heater will be shut off, while everything else works. I have replaced the filter, replaced the hi limit sensor, both with brand-new parts and it is still happening. I have taken the heater relay board out to inspect, and there are no obvious flaws to me and I had also checked all wiring with a multimeter (to the best of my ability - not an expert here), but 240 is going to the heater when it is on. So, does this sound like a heater relay board problem, a main board issue, or is this something else? Edit: Turning power off and then back on will immediately fix the issue for days to weeks until it happens again. Circulation pump seems fine as the circulated water output is strong.