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Thread: Kenmore dryer won't heat

  1. #1
    Patient
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    Kenmore dryer won't heat

    Model Number: 417.84072300
    Brand: Sears Kenmore
    Age: More than 10 years

    Trying to figure out why it will run but won't heat. Heating element = 11.6 ohms end to end, open end to ground, thermistor control and thermal fuse less than 1 ohm, and high limit thermostat at ~54 ohms (all measurements made with no wires connected). The mother board is electronic so I'm not sure if there are any tests to perform there. Anybody got and good ideas?

    Edit: electric dryer, flipped circuit breaker on and off, measure 208 across the outlet.

    I forgot to mention when I turn it on it will heat for a minute or two then quits. If I wait long enough (20-30 mins) I can get it to heat for a couple more minutes and then it quits again.
    Last edited by npm; 05-16-2016 at 12:48 PM. Reason: clarify heater type.

  2. #2
    Doc
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    A couple things pop up.

    The thermistor is way too low in resistance.

    The hi-limit is too high.
    It should be 0 ohms.

    Could be that the unit is overheating so the hi-limit starts controlling the temperature.
    It's contacts are not very good so after a while they can get pitted etc.

  3. #3
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    Thanks for the input. Let me double check tomorrow, I'm probably not calling them by the right names.

  4. #4
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    OK, with the proper names the thermistor control is 60 k ohms (I didn't see the k on my meter the first go round). High limit thermostat was .1 ohm and so was the thermal fuse (I call .1 ohms on my meter = to 0 ohms). I hate to throw $40 + out for a hi limit thermostat on an off chance but maybe that's what I should try. I'm also concerned there aren't any mother boards available, the machine is only 13 years old. Was this some kind of orphan model?

  5. #5
    Doc
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    Your resistance readings look OK so odds are that it is something that is heating up and then opening.

    To try and narrow it down you will have to do a live test.
    Be very careful when doing this as 220 volts is lethal.

    The heater circuit is L1 then the heat relay on the control board then the hi-limit then the heater then the centrifugal switch on the motor then L2.
    Check for any loose or poor connections in this circuit. Could be that heating up a bad connection is killing power to the heater.

    Place your meter on the control board side of the high limit and the centrifugal switch side of the heater.
    Now run the unit if when the heat turns off the voltage drops to 0 then you know the problem is not in the heater or the hi-limit.
    Either the heat relay or the centrifugal switch is the problem.

    If the above two parts are OK then place your meter across the heat relay contacts L1 to relay output from the board. I think L1 is red in this unit (input side of contacts). Could also use the control board side of the hi-limit. This should then be measuring across the relay. This may be easier that trying to do this at the board.

    When running with heat, it should be 0 volts.
    If it jumps to 220 volts when your unit seems to overheat then it is a problem with the relay either bad contacts or bad electronics which control the relay.

    If it stays at 0 volts then odds are that the problem is with the centrifugal switch.

  6. #6
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    Thanks for the good info. It's my daughters dryer so it will take a day or two to get over there and measure some of this.

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