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How to test dishwasher thermostats

Discussion in 'Troubleshooting and Repair' started by XsamX1987, Jun 24, 2017.

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  1. XsamX1987

    XsamX1987

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    Jun 24, 2017
    Hello all ok so my old dishwasher with a manual dial is playing up it gets stuck halfway through the main cycle and it just keeps washing with hot water so I'm kind of going through the parts and it would be nice to bounce some ideas and receive pointers

    Heating element I think is fine if its heating the water and drying

    capacitor 8uf I don't think its this as the motor still drains

    Thermostats I hope it is these as there not to pricey and that maybe the cycle gets stuck because it cant tell its reached the correct temp I have ordered a digital multi meter but I'm not sure what the best way to test them and what I'm looking for to tell me if one is faulty

    The Timer now I really hope it isn't this as the dish washer is old and the timer is not easy to find.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,989
    2,809
    Nov 17, 2011
    It depends on the type of thermostat/thermo sensor. You'd have to find the nominal specs, then you can test the actual specs and decide whether the thermostat is good or not.
    Do you have a cicut diagram where the components are well marked (as this is an old dishwasher, chances are a circuit diagram was delivered with it. Today this is no longe common).
    Otherwise, what is the inscription on the thermostats? This may help finding the technical data. Some good photos may help.
     
  3. XsamX1987

    XsamX1987

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    Jun 24, 2017
    Ok I will hook the Thermostats out today :)
     
  4. XsamX1987

    XsamX1987

    29
    0
    Jun 24, 2017
    Ok so this is what I've found so far

    This is the I will call it 2nd thermostat this sits firmly against the underside of the dish washer with some kind of compound, using the lowest ohms then continuity I think this is always closed/open the left and the right are connected then the top 2 are connected but the top left and bottom left are not same as the right 2
    [​IMG]

    [​IMG]

    This is the first one its sits internally inside the door worrying as it wasn't sitting flush against the plate the same compound had kind of stretched out of place so Its worrying how is it suppose to work if its not sitting snug against the plate to pick up the temperature, same test as be for But like you said Minder contact closure when at temp, so I hooked up my multimeter with clips boiled the kettle then pored water in mug and kind of dunked it in you can hear it make a click when at temp, on ohms 2m it read 1. then as soon as it clicks it goes up a little then drops back down to .000

    Here is a little sketch of the dish washer and where roughly the thermostats sit
    [​IMG]

    So what do you think are they both working, is it maybe not working because the 1st thermostat isn't sitting flush so cant tell when its reached the temp it need to close or open ?
     
  5. XsamX1987

    XsamX1987

    29
    0
    Jun 24, 2017
    Sorry forgot to include its a Zanussi dishwaser ds17 not much information can be found on it, ev thermostat type 9080000 and ELTH K-II 263b t130
     
  6. Minder

    Minder

    3,182
    691
    Apr 24, 2015
    They are common in home appliances, dryers etc, they are N.C. and when temp is reached open circuit.
    They should read close to zero and open when raised by heating somehow.
    Some are used for Reached temperature, others for over-temp situations.
    Normally the temp range is stamped on them.
    M.
     
  7. Alec_t

    Alec_t

    3,060
    834
    Jul 7, 2015
    It should be in good thermal contact with the metal plate. Was it just held with adhesive originally, or is there something to clamp it in place?
     
  8. XsamX1987

    XsamX1987

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    Jun 24, 2017
    the bottom one has a good clamp hold it in place the one on the door plate has a flimsy bit if thick gauge wire and there was a load of compound around it but like a 10mm gap between the thermostat and plate
     
  9. Minder

    Minder

    3,182
    691
    Apr 24, 2015
    That could be a problem, there is heat conducting compound but the spacing is minimum.
    M.
     
  10. Alec_t

    Alec_t

    3,060
    834
    Jul 7, 2015
    Can you safely improvise a clamp and thermal coupling for the stat, to see if the machine then works ok?
     
    Harald Kapp likes this.
  11. XsamX1987

    XsamX1987

    29
    0
    Jun 24, 2017
    you guys are the best, ok so I put the thermostat back in place I recoated it in some cpu thermal paste then cut down a piece of wood about 2inches that now pushes the stat against the plate put it all back together put it on full cycle it now runs with out stopping those 3 times during main cycle :)
     
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