I spent a couple hours last night in the lab working on a friend's specialized refrigerator made for chilling wine (probably called a "wine cooler" but every time I say that I can't help but think Bartles & James). It stopped working, and when he pulled it apart noticed that the fan on one end wasn't spinning and turned with some resistance. When he showed it to me it was apart on a counter and I offered to take it home to the lab for some measurements.
It's a fairly simple device, little more than a Peltier cooler, power supply and thermostat. There's two of these Peltier/power supplies pairs, one on each end of the cabinet and both are controlled by a single board that provides buttons to set the desired temperature and turn the internal lights on-and-off.
Taking voltage measurements at the various connection points of the power supply board on the misbehaving end confirmed that it wasn't putting any power out to the fans, and temp measurements on the hot and cold sides of the Peltier showed virtually no change. I compared this to power and temperature measurements on the other end and things were more of what you'd expect.
Given this I'm fairly confident that the power supply is shot, and at least one of the fans are bad. I'm guessing that the bearings are failed on one of the fans, and either the fan or the Peltier or both pulled too much current and overloaded the supply. I would expect this to trip a breaker or blow a fuse, so I went hunting for such things on the power supply board.
I located two fuses but they were both intact. Hmm... It would not be out of the question for something else to fail on a board like this, and after a few web searches I found a lot of similar stories about coolers like this failing. Some had detailed technical discussions and even successful repairs, most repairs consisting of replacing some or all of the electrolytic capacitors and/or the power transistors.
So chances are that replacing or repairing that power supply board is all that is needed, but something that bugged me the entire time is that the control panel never lights-up. It has a two-digit LED display for the set temperature, and one of the buttons should toggle the internal lighting and neither of these things lights-up when power is applied. Since this board appears to contain the thermostat function it's possible that it could be malfunctioning and sending the wrong signals to the power supply that appears to be failing. My confusion is compounded by the wiring to this control panel because it's not crystal clear to me where it's power comes from.
There's a connector that goes to the temperature sensor, two that appear to go to the internal LED's and then two more, each connected to a 3-pin connector on each power supply which I assume controls the cycling of each Peltier. So where does the power for the control panel itself and the interior LED's come from? It must come from the power supplies, but there's no clear positive/negative connection to one of the supplies, just these two three-pin connectors. It's possible the control board gets it's power from these 3-pin connections but if that's true why isn't it lighting-up if one of the power supplies appears to work?
Without knowing the answer to this I can't be 100% sure replacing the dubious power supply will fix the cooler, so I started thinking about ways I could isolate the control board from the equation and at least increase my confidence that the power supply in question is bad and it's not just getting bad instructions from a faulty controller.
This was fairly easy because I was able to confirm that the "working end" continued to behave the same even if I removed the connection to the controller board. I also noticed at this time that there's two LED's on the power supply board (red and green) and that they both light-up on the working supply. When I repeat the same test on the questionable end, there's still no power at the outputs, no temp change across the Peltier and neither of the LED's illuminate.
At this point I'm confident the power supply is toast. This doesn't tell me anything certain about the control panel board though, and it still leaves me puzzled at to why the controller doesn't light-up.
I was able to find replacement power supplies that look to be similar for around $100 delivered. This would be the easiest thing to try to fix the cooler (coupled with at least one replacement fan), and I'm confident that the power supply needs to be fix/replaced, but even with a new supply I can't be 100% sure the unit will work because I don't know what is up with that control panel board. My biggest concern is that something in that controller is bad and when I attach a new power supply to it, the new supply will get damaged by a fault in the controller. I'd really like to see the controller work before advising my friend to spend $100 on a new part.
This is complicated by the fact that I can't locate a drop-in replacement for the controller board, so even if the new power supply isn't ruined by a faulty controller, I can't simply say "spend another $x dollars to finish the job", and if I can't repair the controller board it might just be a waste of money to replace the power supply.
The whole time I've been working on this my mind wanders-off designing replacement electronics instead of trying to understand/diagnose the broken ones. I'm sure I could design a replacement that would be more serviceable and probably less expensive than the replacement parts I've been able to find (not to mention the parts I can't find). But that is a much more time-intensive project, something I don't honestly see me finding time to complete until next winter.
I could also try repairing the faulty power supply first, which might only require a few dollars worth of parts (most or all I probably have on-hand somewhere). But here again there's a significant time bump involved in that approach that I don't know I'll have, and it's entirely possible that the repair will fail and we'll be back at ordering a $100 part.
I didn't like any of these options so I decided to sleep on it.
In the morning I had one more idea as to how to test the control panel board. Maybe it gets it's power from just one of the 3-pin leads coming from one of the power supplies, and maybe it's the connector that is connected to the bad supply? This seems weird to me but honestly there's a lot of things about this device that seem weird, and I seem to remember that the two 3-pin connectors were labeled A and B or 1 and 2 or something that indicates that the connector that goes to the dead supply is the "first" one. So if the controller gets it's power from only one of the supplies, then it seems reasonable that it would be getting it from the dead one.
So I'm thinking my next step is to swap the 3-pin connectors and see if the control panel lights-up. If that happens I can be a lot more confident that swapping the bad supply and fan will fix the thing. If not, then maybe I can try to learn more about the controller board (maybe just manually trace it out) and find some way to reliably test it. Until I know it's condition (or can find a replacement) I just don't feel comfortable recommending my friend throw any money at the thing.
(in the meantime I'll keep dreaming-up an open replacement as well)
Jason J. Gullickson, 2026