Ptc thermistor in a wine refrigerator

Discussion in 'General Electronics Chat' started by sherlock ohms, Dec 29, 2015.

  1. sherlock ohms

    Thread Starter New Member

    Dec 24, 2013
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    Wine fridge stopped cooling. Compressor would not start but would get hot. Found a post on line where a guy with a similar problem pulled the relay/overload off the compressor and found a little round ceramic disc which appeared spotted on one side. On a whim he reversed the disc, reassembied relay housing, and Voila!, the beast began cooling.
    Question: im a self-learning amateur. This littlt disc might be a thermistor i think wich will initially allow current flow to the start windings. But why would reversing its direction in the relay housing have any influence on whether current was able to flow through it??
    Many thanks in advance for any kind assistance
     
  2. sailorjoe

    Member

    Jun 4, 2013
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    Sorry, Sherlock, but there's just too little to go on here. The little disc could have been a thermistor, an RTD, a capacitor, or a fluegalfram. Reversing it may have done something or maybe nothing. It's just too random. We don't know what would have happened if he had just removed it from the circuit altogether.
    You could try replicating what he did. You could look for more ideas on line. You could call a repairman.
    How would you like to proceed?
     
  3. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Sherlock Ohms. Now why didn't I think of that? ;)
     
  4. sherlock ohms

    Thread Starter New Member

    Dec 24, 2013
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  5. sherlock ohms

    Thread Starter New Member

    Dec 24, 2013
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    I don't agree it's random. I followed suit and flipped the little disc around. My compressor kicked on and the fridge fell to 45 F in minutes. So reversing the disc DID change something in the circuit. I,m just not schooled enough to understand what or why.
     
  6. sherlock ohms

    Thread Starter New Member

    Dec 24, 2013
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    I have to confess i like it too. As an amateur learner, who likes trying to understand the electrical intricasies of household devices, I figure the Baker Street sleuth would have enjoyed the logic and beauty behind circuits, just like me.
     
    cmartinez likes this.
  7. #12

    Expert

    Nov 30, 2010
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    Neither am I, and I fix 'em for a living! That's probably a lie, but I never bothered to autopsy one. The last time I looked, the local appliance parts store had several hundred of those ceramic starters in stock. That tells me they fail...a lot! I just replace it, the machine starts running, and that's the end of it.

    You can replace your starter and autopsy the old one...or buy two and autopsy both a good one and a bad one. From here, we really can't tell if the only thing that happened was disturbing the dirt so it made contact again.
     
    Johann likes this.
  8. sailorjoe

    Member

    Jun 4, 2013
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    Well, then, congratulations, Sherlock, you've solved another one. Good on ya!
     
  9. sherlock ohms

    Thread Starter New Member

    Dec 24, 2013
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    Thanks for writing. Do you think this ceramic disc is a ptc? Would a ptc allow current flow only in one direction? I like your thought that maybe the surface was cleaned up a bit in handling and the reversal of the disc was not the prime factor.
     
  10. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    I think it was a bad solder job to start with. Resoldering is coincidental with flipping it around.

    I bet if you flipped it again, it would still work.
     
  11. Externet

    AAC Fanatic!

    Nov 29, 2005
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    When the PTC pill was flipped, the electric contact points from its holder contacted another undegraded area of its surface and worked. Agree with joey that should work if flipped again.
     
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  12. #12

    Expert

    Nov 30, 2010
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    I always get those mixed up. PTC means hotter = more resistance? If true, then yes, it's a PTC. It allows start current for just about a second, then heats up and sort of disconnects the start winding from the power. The low mass of the ceramic means the PTC will reset to the, "current available" condition in less than a minute, and refrigerator thermostats usually stay, "off" for several minutes during normal operation. They used to use current relays for this function. They don't need a quiescent time before they will re-start. They also failed occasionally. I have installed about one, in my whole life, but I mostly work on machines that are way larger and use massive start systems. Some, "hard start" kits contain a capacitor with a PTC already attached.

    Let me try to put this in perspective. When I worked at Sears, each parts bin was labeled with a, "minimum low stock" number.
    For instance, electric water valves for ice makers, MLS=3
    95405 v-belts for clothes washers, MLS=6
    When I see a parts bin with over 200 ceramic starters, I know immediately that they sell a LOT of them.

    ps, "only one direction" implies a DC circuit. False in this case. This thermistor is a time delay device which passes AC current. It is merely a very irritable resistor that refuses to work for more than one or two seconds at a time.
     
    sherlock ohms likes this.
  13. sherlock ohms

    Thread Starter New Member

    Dec 24, 2013
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  14. sherlock ohms

    Thread Starter New Member

    Dec 24, 2013
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    Terrific answer!! This really makes it so much clearer. Many thanks.
     
  15. sherlock ohms

    Thread Starter New Member

    Dec 24, 2013
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    Thank you for this important info. I,m beginning to see things much more clearly.
     
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