Fan-driven mini coke fridge, troubleshooting help?

Discussion in 'Technical Repair' started by solderboy, Jun 20, 2016.

  1. solderboy

    Thread Starter New Member

    Nov 12, 2014
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    So I have this, I think is a Koolatron mini fridge that for the 2nd time suddenly stopped cooling, even though the fan works. (not even sure how this thing cools with just a fan and no cooler liquid).

    It should be mentioned that the led does not go on when powered up, and stays off no matter what setting. But this used to be the case when it worked last time as well. Last time I opened up the fridge case, cleaned out the fan, and wiped the 'coil' (or whatever that cylinder shaped square in the middle's called), and even removed the coil then put it back, and when putting the fridge back it started cooling again, but not this time around.
    When I this time around opened it up to try to repeat the last time's process, it still won't cool, even though as usual the fan works and has been cleaned. (again, last time's process was more random than specific, not sure what 'did it').

    Also, the power switch, when set to the left (i.e. "Warm") it turns off the fan instead, and there's no 'click' sound between the different switch settings suggesting some part of the switch is lose (there might be a slight rattling noise inside), is there any suggestion or red flag based on that? Basically both 'off' and 'Warm' are now 'off'.

    Or just overall, what is a likely cause for it not cooling when it seems to be running on no more than a fan which is working?


    I've supplied some pictures which may or may not be helpful, but if another picture could help I'd be happy to provide it if someone let me know.

    Thanks in advance
     
  2. BobaMosfet

    Senior Member

    Jul 1, 2009
    137
    19
    What you describe sounds like a Peltier module. When you run it one polarity, it cools, when you run it the other, it warms. They turn the fan off during warm, so the heat is not dissipated, whereas for cooling, they must get the heat away from it or it won't function.

    If the fan runs, it thinks it's in cooling mode, but if it doesn't 'cool', then either the wiring to the peltier module has failed, or the module itself has failed. You cannot get the modules wet, or it can compromise their ability to work, cause them to fail. If you run it in warm mode, does it heat? If not, check connections and if they are good the peltier module has completely failed.
     
  3. solderboy

    Thread Starter New Member

    Nov 12, 2014
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    Nice start, do you think it's easy to replace a peltier module, or perhaps 'fasten' the wiring into it, or is it even feasible to think of? These aren't expensive fridges, but I just resent throwing out stuff that 'can' be fixed dyi.

    And nope, it doesn't heat in warm mode. Also, does it matter that the leds don't light up irrespective of setting?
     
  4. jellytot

    Member

    May 20, 2014
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    The object in "coil.jpg" appears to be a TEC module (aka Peltier module, aka Thermoelectric module) (the thing attached to the wires), with a heatsink attached (the silver thing with fins). TECs are generally pretty cheap, depending on the size. The model of the TEC is usually written on one of the sides. If you can verify that it IS broken, you can get several models of TEC off of ebay (from China) for a few bucks. Be prepared to wait forever for them in the mail, though. Also, something that is throwing me off is that there are 2 screws in the heatsink, which imply the screws are going though the TEC. I'm not sure you can drill through a TEC; I've never tried it. So the TEC in your fridge may be custom. Oh, by the way, never run power through a TEC without a heatsink attached to the hot side, or you will burn out your TEC.

    I doubt your TEC is broken, anyway. It sounds like the switch may be broken. If you know how to use a continuity tester, you could know for sure. But I see capacitors in the insides. I don't know how big those are, but if they are big enough they could seriously hurt you (even if the fridge is unplugged).

    You may want to check Aliexpress/eBay/Amazon or similar sites to see if it may just be better to get a new unit.
     
  5. Tonyr1084

    Well-Known Member

    Sep 24, 2015
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    If the switch rattles or doesn't feel like it's switching action is behaving in a positive manor then I'd start there. If there are any fuses - check them. But back to the switch, if when you switch it there's no solid click then it might not be switching. If it's a multi-pole switch then part of it may be defective while switching the other part. In other words, it may be switching the fan on and off but not switching the Peltier element.
     
    KJ6EAD likes this.
  6. wayneh

    Expert

    Sep 9, 2010
    13,624
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    On the LED issue, it could just be a dead LED. If you can remove it, we can tell you how to test it and replace it.

    Your cooler should be fairly easy and cheap to repair as long as the circuit board is working.

    I agree with starting at the switch, since you know there's something not right with it.
     
  7. solderboy

    Thread Starter New Member

    Nov 12, 2014
    21
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    Thanks for the switch suggestions. Will see if it's possible to access/remove it since it's really narrow space packed with cables, will get back if anything gives.
     
  8. crutschow

    Expert

    Mar 14, 2008
    16,538
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    Can you verify whether power (voltage) is getting to the peltier module?
     
  9. solderboy

    Thread Starter New Member

    Nov 12, 2014
    21
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    Thanks for the suggestion, assuming i'd need a multimeter, or circuit tester for that?

    Otherwise, to continue where i left off, the power switch is fused/glued to the PCB that controls it, so seems irreplaceable, but there's clearly something lose in it, as mentioned above there's.no click, and turns off under the 'warm' setting, again seems to be no way to remove it, or even find the right part.

    Btw, it seems to cool slightly mainly where the floor meets the back, not nearly enough to cool the interior. Kinda wonder how the cooling mechanism works, there being just a fan/no liquid, i think..
     
    Last edited: Jul 29, 2016
  10. Tonyr1084

    Well-Known Member

    Sep 24, 2015
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    I recommend googling "How does a Peltier module work?"

    From what I saw (and I'm not the expert) it moves heat energy from one side to the other. The module can be powered or used as a power source. Using it as a powered module it will move heat from one side to the other. In other words, any heat energy in the cooler will be moved away (pumped away) and ejected by the cooling fins and fan.

    Used as a power source, if the "Hot" side is warmer than the "Cold" side then electrons will begin to flow. The greater the difference and the greater the surface area (size) the more power can be generated. However, as generators they are not very powerful. However, I recall a young girl who took Peltier modules and mounted them on a copper pipe. They were hooked up to super bright LED's and she made a flashlight that worked just by the user's body heat from when it was held in the users hand. So they CAN be useful as small generators or power sources.

    In your cooler, power is applied and it begins transferring heat from inside the cooler to the outside. Many people think of heat as being hot. Relatively speaking, ICE can be hot. If compared to something much cooler. Kelvin temperature is another thing you might google. Absolute zero (Zero Kelvin) is when all electron activity ceases. There is no such known thing as "Colder" than zero Kelvin. So at levels above zero Kelvin there is electron activity in atoms. Peltier modules work on that difference, and a good Peltier can make ice. I didn't say a 10 pound block of ice - I said it can make ice. Frost. Something cold enough to condense water. Depending on how big the module is and how much power is pushed through it.

    Peltier can't replace compressed freon gasses yet, but for small applications such as a cooler (ice chest) they can keep things cold - to some degree. I have no experience with them yet.

    You asked if you'd need a volt meter to test your module. Well, I don't know how to test them but then again, Youtube has videos on that as well. A meter will likely be a good investment. It can be used for so many other projects, and they're not expensive. A good cheap one can be purchased in any electrical department of any big box home improvement store. Even smaller stores will likely have one. You can even get them at automotive stores. I keep one in the glove box for such cases as finding a bad fuse or checking battery voltage. In the house they are useful for checking resistors (since I'm partially color blind - makes reading color codes difficult). Some meters can check capacitance. They check current but mostly milliamps. More and more I'm seeing them able to check up to 10 amps - and they are all not very expensive.

    Using a meter you can check to see if you're getting power to your Peltier module. You can also check voltages at switches. A voltage across a switch that is in the "ON" position will tell you the switch is defective (not truly ON). So get yourself a meter. Even a cheap meter can be useful. I keep a Radio Shack meter in my car. Good enough to check the battery, fuses and light bulbs.
     
  11. Bryanofalltrades

    New Member

    Aug 16, 2017
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  12. Bryanofalltrades

    New Member

    Aug 16, 2017
    3
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    hey guys I came here looking for help fixing my own circular can of coke fridge but didn't find much info. tore it all apart and thought I'd show a pic.

    my issue was the limit switch mounted onto the Peltier module was bad. jumpered it and everything took off and cooling. my led which didn't work now does as well. there are wires next to the condenser fan that may be giving the rattle noise.

    I was really missed to start out this process. just bought the thing at an auction which only listed it as needing a cord. (likely broke and they tossed the cord making the problem seeming easier! lol)

    Idk how hard it will be to find this switch but for now I'm just going to jumper it! hope this pic helps!
     
  13. Tonyr1084

    Well-Known Member

    Sep 24, 2015
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    Can you get a close up of the thermal switch? It's possible you could find one at an appliance repair store. It might be one that shuts off when temperature drops to a pre-determined level, meaning it's a closed switch until it is too cold. Cold opens the switch. If you're jumping it and it's working then the switch is likely bad. I said LIKELY. I don't KNOW it's bad, just coming to that conclusion based on the picture you painted.

    Show us a close-up of the switch. A couple pictures so we can see it from different angles and so we can read the numbers on it.
     
  14. Bryanofalltrades

    New Member

    Aug 16, 2017
    3
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    mine doesn't get very cold either. must be low on the Freon or whatever is used.
     
  15. wayneh

    Expert

    Sep 9, 2010
    13,624
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    These little coolers don't use gas recompression cooling, they use a solid state cooler known as a TEC (thermoelectric cooler) or Peltier module (same thing, two names). The device in the photo is a thermostat. Since it's labelled 85°C, it must have been designed to detect a problem of some kind (such as a stalled fan or blocked airflow) and shut the device down to protect it from getting any hotter. Jumpering this device is like putting a jumper around a fuse. It solves the immediate problem but eliminates the protection this device was designed to provide. If it has failed open (non-conductive), just get another one and replace it ASAP before your cooler overheats again.
     
  16. chickwithav8

    New Member

    Tuesday
    4
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    Thanks guys, all of this helped me take apart my fridge and I found that my 2 fans work but the circuit they're plugged into doesn't. Any way I can jump something somewhere to amke them work?
    I plugged the little to-the-inside fan into some circuit that wasn't being used and is labeled LED. It was making the fan go backwards so I just flipped the fan around. Waiting to see if this cools the inside of the fridge enough. However the larger to-the-outside fan still isn't working so there is nothing to cool the heatsink........
     
  17. Tonyr1084

    Well-Known Member

    Sep 24, 2015
    1,364
    300
    Guesswork is not advised. Rather, get a wiring diagram if you can. If not then you'll have to make your own diagram by tracing out the circuit yourself. Then you can post it here and we can try and help. But to try and jumper something - you could cause more damage than you're fixing. I don't think an LED circuit can or should be expected to run a fan. If the fan is running backwards - something's wrong. As yet we don't know what. If another fan isn't working - again, we still don't know why. So either just buy a new unit or do the work and come up with a reliable schematic. Check it again, then check it a third time to make sure you've got everything right and represented correctly. Nothing worse than working from a faulty schematic. So try real hard to get the schematic from the manufacturer if you can.
     
  18. wayneh

    Expert

    Sep 9, 2010
    13,624
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    This thread may help you. It's long now, but there are lots of ideas, a few schematics, and so on.
    It might all be summarized in one phrase: "Replace the capacitors."
    https://forum.allaboutcircuits.com/threads/repair-thermoelectric-cooler.101748
     
  19. chickwithav8

    New Member

    Tuesday
    4
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  20. chickwithav8

    New Member

    Tuesday
    4
    0
    This photo was missing and that's not the emoji I was going for
     
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