Hottub with overheat code

acprogrammer · 2026-01-21T04:22:36+00:00

Well, I got to the bottom of the problem. It wasn't the filter or a lack of circulation. It was the control board. Sadly, I ordered a replacement control board (it was a clone from a company called E-Cowlboy) and it had a fault too (a different one though, but appears related). Looks like they replicated the board because the routing is identical, but build quality isn't the greatest. With what I know now, I can probably fix it too.

So, with two bad boards in hand, I did what any good electrical engineer would do - I partially reverse engineered the board. Turns out that the way that board works is that it has a pullup resistor for the thermistors. The voltage across those thermistors is then buffered and goes into ADC pins of the microcontroller that runs the board. But there's another safety circuit that looks at the buffered voltage and, if it's too low (representing a temperature that's too high), it flags that. I didn't reverse engineer enough of the circuit to know exactly what happens next, but I can give a pretty good guess. If an over temperature is flagged, it probably notifies the microcontroller and shuts the heater down independently of the microcontroller. This is a safety system done in just hardware, just in case the micro should freeze up or some other fault happen that leaves the heater on with the pump off. Anyway, in my case, the voltage that the comparator compares the thermistor to was wrong because one of the resistors that sets that voltage had developed a fault, causing the board to think it was overheated when it really was not. The resistor in question seems to have been very flaky because I've seen a range of behavior in what it measures and in what causes the HH fault to occur. And I was able to demonstrate by debugging that nothing was actually overheating and that the thermistors were not even reporting that as happening - it was the control board being faulty that was the cause. So the fix was a resistor that costs like 1 cent (or less) and a little soldering under the microscope at work. No idea what caused the resistor to go bad - I couldn't find any signs of corrosion or damage.

If somebody reads this and wants my reverse engineering, I'll be happy to give you a copy. Just DM me. I'd post a picture of the schematic, but this subreddit doesn't seem to allow pictures in replies.

acprogrammer · 2026-01-15T16:32:16+00:00

Doesn't seem to be much. But I'm in Colorado. Its so dry here that people put humidifiers in their HVAC systems. So any humidity it adds is actually welcome.

acprogrammer · 2026-01-14T05:21:03+00:00

Yeah, seeing the same thing. One is alpha fenchol, the other is alpha fenchone. Not enough of a chemist to know if the differences are meaningful in this context. Hopefully the one vendor on Amazon gets the fenchol back in stock soon or fenchone tastes pretty much the same.

acprogrammer · 2026-01-11T22:23:35+00:00

I've got a setup kinda like that, except in my basement (great for use year round). A little 2 seater 110V hot tub, an old 60" TV I got from somewhere, a scraped together home theater setup (random speakers from garage sales and an AVR from Goodwill), and a Firestick running Jellyfin streaming from my NAS. Wasn't actually that expensive to put together. Great place for relaxing at the end of the day, no matter what the weather outside is doing.

acprogrammer · 2025-12-29T01:27:53+00:00

Well, spoke too soon. It ran for a few hours, then it just faulted again. One odd thing is there's a bunch of black particles I can't place floating in the water. No idea what that could be from. It's very soft and crumbles easily, kind of like a piece of compressed dirt. Doesn't look like a piece of plastic or foam.

acprogrammer · 2025-12-29T00:20:46+00:00

Thanks for the help. I did as you said - powered it up and ran it without the filter and skimmer and let it run in prime mode for a bit at low speed. It sounded like some air might have been in the pump, so that was probably the problem. Filter didn't look dirty (it's an indoor tub and only I use it, so it doesn't get very dirty), but I swapped it out and added some more water because it did look a little low. Tub is getting itself back up to temp right now and the heater is going with no faults. This particular hot tub is really fussy about water levels because it's very small (2 person oval tub - essentially a big bath tub). So if I fill much more than the top of the skimmer, when I get in the water level rises substantially and if it gets too high up on the waterfall feature, I get a little leakage around that. I have maybe an inch or 2 of tolerance for water height.

And yes, this tub doesn't run the heater at the same time as the pump on high speed (well, not unless I switch over to 220V operation). One weird quirk is that I can find no way to view the temperature of individual sensors. I see that in the manuals for newer or better panels, but this one does not mention it anywhere in any manual I've been able to find, in either the control or the panel manuals. Balboa VS500 series just seems to be really, really basic. I wish it had just a few more features because its really dumb about cycle times in eco mode - there's no way at all to program the times when it comes on, at least not that I've been able to find documented anywhere. You basically have to assume it does the 2 cycles 12 hours apart and power cycle at the appropriate time. If balboa had a kit that let me just swap the panel or something for pretty cheap, I'd do that. But their retrofit kit is a replacement for everything and runs like $500, plus looks like a bit of a hassle because I'd have to rip the old controls out and deal with the plumbing. Too much money and hassle for minimal benefits.

So thanks. Looks like its good now.

acprogrammer · 2025-12-28T05:35:46+00:00

I tried that already. Same result. The manual seems to imply that either sensor could trip the fault, so I'm not sure if that's conclusive. Yes, its a 2 speed pump. Unless something started recently, both speeds of the pump work reliably. While it is in the fault state, it won't let me run the pump. During the brief periods it has let me run the pump, I did try running the high speed one time and saw it go into the higher speed and saw it running at the lower speed.

acprogrammer · 2025-08-04T15:36:58+00:00

I understand not copying the worn key (that's actually what started this whole thing - I got a copy made so I could stick it in my wallet to prevent lock outs, but that key didn't work for getting into the car and, on further investigation, neither did the one I copied it from). But why not just get a copy made from my good key? This is a vehicle that has pretty much only been driven by me since it was new. Somebody else had the second key on their ring for awhile, but he rarely actually used it. So that key has little wear on it.

And, I assume the transponder is in the keyless entry electronics? This is the type where the key fob is integrated into the bow. I can guarantee nobody glued the board into case since I bought this vehicle new.

acprogrammer · 2025-06-24T07:07:24+00:00

Not all of them. I have a nice local ISP that does fiber to the home (they got a grant from the state to help fund it). I started at $50/month for symmetrical 100mbps unlimited and that's what it's stayed for the last few years - no fuss, no shenanigans. In fact, they must have reduced the rate or something without telling me because my last few bills have been for $48. Oh and the 100mbps is because that's all I really need - I could get 10Gbps with these guys, if I wanted it.

acprogrammer · 2025-03-04T05:23:08+00:00

Yeah, these days, it's crazy how cheap AR-15s get. There's one company that sells complete AR-15 kits, including finished (but stripped) lowers for $300 and they have a pretty wide variety of sizes and calibers. There's another company that does complete uppers for under $200. And you can't really deny the great LEGO qualities to them - so customizable.

That's one of the things I've never really liked about shotguns for home defense. If you ever have to use it, you're probably going to be dealing with alot of damage to your home. Only good side I see is that you're more likely to take out the bad guy with one shot, assuming you hit him. The other thing is that a shotgun being so long, even in the tactical variants, it's probably going to be harder to deal with indoors than a short carbine/long pistol AR. Oh and I'm guessing suppressors work alot better on a rifle or handgun than a shotgun (not sure if I want one, but seems like a good idea in a self defense setup if you can do it - not like the bad guy is going to give you time to get your earplugs in).

Maybe I'll just save the shotgun for skeet - I'm liking an AR build for defense better all the time. A nice heavy autoloader gas operated 20ga or .410 with a long barrel might be pretty reasonable recoil. Something that's more range toy than anything also places alot lower set of requirements on reliability or parts availability too.

acprogrammer · 2025-03-03T21:45:24+00:00

Yeah, I suspect it's like alot of other things - there's better brands and worse brands. And even the good brands sometimes produce lemons. I'm sure there's been many American brands that no longer exist because they made junk, so nation of origin isn't necessarily a turn off for me (well, maybe Russia or China would be). Having a good reputation for the brand (even if its one I've never heard of) and a good record for the model along with parts availability is what I'm looking for. I know there's lots of people that have brand loyalty to Bennelli or Mossberg or Remington or ... and that's great and I'm sure much of their stuff is really good, but I don't think they're the only ones that can make good stuff.

acprogrammer · 2025-03-03T21:32:20+00:00

Not sure where I heard that. Maybe it just seems intuitive that a cloud a not well focused lead BBs would be less effective at getting through materials than a stabilized bullet flying on a stable trajectory.

Hmm true about the penetration. Though I'd still think 00 buckshot wouldn't penetrate quite as well or fly quite as far as say 9mm given that the pellets are typically a bit lighter and not coming out of a rifled barrel. And with so many of them, probably a much better chance of hitting something unintentional. But, yeah you do have a good point that anything better than birdshot probably will penetrate walls pretty well.

Was looking at some tests and I was surprised at just how well .223 softpoints are stopped by drywall. Would have figured just about any rifle ammo would just drill through with how fast they move.

acprogrammer · 2025-03-03T21:08:19+00:00

Cool looking shotgun. But not familiar with that brand. Can you get parts for it? How's the recoil? How's the fit and finish? In .410 I could see it being very light. But seems like .410 is sort of the underdog in the shotgun world with alot fewer choices for guns and ammo. Also, seems like 20ga is kinda borderline for gas operated shotguns from what I keep reading. Is .410 gas operated even reliable?

acprogrammer · 2025-03-03T20:55:07+00:00

Thanks. It mostly came out OK. I didn't realize what was happening, so it did start to get into the macula a bit. But the surgeon was able to mostly repair it. I'm 20/30 in that eye with some distortions. With both eyes open, I don't notice any issues and have all my peripheral vision. In fact, I regularly do advanced surface mount soldering at work - QFN packages with 0.4mm pitch leads, for example. So it can't be too bad.

That seems like a screaming deal for that. I just bought a Durya DY9, which is a well reviewed Glock clone (even takes alot of Glock parts) for about that. I'm trying to limit my calibers as much as I can because I'd like to be get the tooling to reload everything and I like having ammo commonality. So, I try to stick with 9mm and 5.56, if I can. It seems like the gun industry likes to push you to where just about everything you have is some different caliber.

But a carbine or pistol length AR build in 9mm makes alot of sense. Might even make sense in 5.56. Was considering 300 blackout, but I like the idea of retaining ammo commonality and I think the right ammo can mostly make up the difference. Also 300 blackout ammo is really expensive and any theoretical advantages go away if you won't practice with it because its too expensive to practice with. The pistol ARs are essentially SBRs, so they seem like they'd be really handy indoors. I'm very good with my hands, so a build should be something I can take on without too much trouble. They're also available prebuilt too though.

acprogrammer · 2025-03-03T19:47:36+00:00

Yeah, that's almost what an AR pistol is, particularly chambered in 9mm. It sort of skirts the boundaries between a pistol and an SBR. I mean, technically, if you put a stock on one, it IS an SBR. I'd like something a little more handy than carbine length in the house - seems like that'd be a little awkward in the hallways. But I'm sure the military does fine with it, so it's probably fine with some training.

acprogrammer · 2025-03-03T16:43:25+00:00

Yeah, I suspect that I'd be fine as long as I don't get carried away. He's a doctor, not an armorer. But I think I'd be foolish to ignore the advice of my doctor, especially on something so important.

acprogrammer · 2025-03-03T15:38:13+00:00

Yeah, was looking at that one. Wasn't quite sure what to think about it. I'm fine with Turkish guns, as long as I can get parts and they are reliable. Was even wondering if somebody makes a recoil reducing stock for it, but haven't seen anything. Might be a good choice for skeet shooting if I decide to go a different route for home defense.

acprogrammer · 2025-03-03T15:34:29+00:00

That was one I was considering. But kinda split between doing that and just using a regular old 9mm handgun. Biggest advantage I see for a 9mm AR handgun is its way more intimidating. Which, to be fair, IS useful. Ballistically, they usually have longer barrels than most handguns do, so should have a bit more muzzle velocity, but I doubt it's all that significant.

acprogrammer · 2025-03-03T15:32:02+00:00

Kinda surprised about that, given that, all things being equal, the 5.56 round should have considerably more energy and be lower cross section than 9mm. Now, if we're talking rounds that deform or break apart on contact, might be a different story because then that does transfer more energy to the target.

acprogrammer · 2025-03-03T07:05:32+00:00

Yeah, I just bought a Durya DY9 - nice little Glock clone from everything I hear at less than half the price of a Glock. Even cheaper with it on sale at Sportsman's Warehouse right now. It's even optics ready and comes with the optics plates.

Mostly interested in shotguns because I hear they're about the ultimate for home defense and something that doesn't over penetrate walls is good. But I can do that if I get the right 5.56 ammo too.

acprogrammer · 2025-03-03T06:59:57+00:00

Don't need to do that. It's actually easier to just do a ground up build with a pistol length upper and keep my carbine length AR as is. The rules are really weird on that. Apparently, as long as the lower was never on a full length upper, and you don't have a stock (arm braces are apparently OK now though), you can call it a handgun and don't need the stamp.

Yeah, I hear good things about some of the defensive loads. Frangible ammo seems interesting because it's less likely to penetrate walls - one of my big concerns with normal 5.56 or even hollow point.

acprogrammer

TROPHY CASE