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Kenmore Electric Dryer: Power Resistor Replacement

Our long-suffering and much-repaired Kenmore clothes dryer didn’t shut off, with the heat on and the timer failing to advance from whatever position we set it to; the clothes were plenty dry and scorching hot. I tried “timed air dry” to eliminate the heater from the problem and found the timer still didn’t advance.

Referring to the wiring diagram may be of some help:

Kenmore clothes dryer 110.96282100 - wiring diagram

Kenmore clothes dryer 110.96282100 – wiring diagram

The timer motor is in the next-to-bottom ladder rung. Its BK terminal on the left connects to one side of the 240 VAC supply and the switch just to its right connects terminal TM to either the neutral AC line (thus unbalancing the 240 VAC line by a smidge) or to through a 4-ish kΩ resistor and the heater element (essentially zero, on this scale) to the other hot line; the resistor thus dropping 120-ish VAC.

The various switches around the timer collect nearly all the wiring in the dryer:

Kenmore dryer - timer wiring

Kenmore dryer – timer wiring

A closer look at the back, minus all the wiring:

Kenmore dryer - timer backplate

Kenmore dryer – timer backplate

The motor comes off easily enough, revealing the fact that it’s not just an ordinary (i.e., cheap & readily available) timer motor:

Kenmore dryer - timer motor pinions

Kenmore dryer – timer motor pinions

Hotwiring the motor through a widowmaker zip cord showed it worked just fine. For reference, the upper pinion rotates at about 45 sec/rev, the lower pinion takes maybe 1 hr/rev, both counterclockwise.

Reassembling and hotwiring the complete timer showed it worked just fine, too.

Poring over the wiring diagram suggested the power resistor might be open and, indeed, it was:

Kenmore dryer - power resistor failure

Kenmore dryer – power resistor failure

The raised zit near the front shouldn’t be there:

Kenmore dryer - power resistor failure - detail

Kenmore dryer – power resistor failure – detail

Apparently, the resistive element broke at that spot, burned through the thermoset plastic case, and failed safe.

Introducing it to Mr Disk Sander revealed a cavity below the zit, surrounded by the remains of the resistive element:

Kenmore dryer - power resistor - cut open

Kenmore dryer – power resistor – cut open

You can get a replacement resistor from the usual suspects for prices between $20 and $40, plus or minus shipping, but their pictures look a lot like an ordinary power resistor inside a length of heatshrink tubing, rather than the molded OEM part. I don’t put much stock in reviews & comments, although they seemed to suggest you get, indeed, an ordinary power resistor.

I didn’t have a 4.7 kΩ power resistor in my (diminished) collection, so I soldered a giant 1.5 kΩ cylindrical resistor in series with a small 3.5 kΩ sandbox, wrapped them up, and tucked them under the front panel’s ground wire:

Kenmore dryer - expedient power resistor

Kenmore dryer – expedient power resistor

A small box of resistors should arrive in the next month and I’ll re-do the repair with a bit more attention to permanency.

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  1. #1 by madbodger on 2018-01-24 - 09:44

    I had the control board on my fridge fail late one evening, leading to much hand-wringing about how the ice cream was going to melt. It turned out to have a bad solder joint on a relay, and a burnt power resistor. I didn’t have the right resistor on hand, so I made one out of eight smaller resistors and ordered the correct one. Since my home-made array dissipates the power easily, it has run for years with no issues and is still in place.

    • #2 by Ed on 2018-01-24 - 11:24

      I half-expected the smell of electrical death from behind the control panel, but so far it’s chugging along just fine.

      Oddly, the Start button now requires a noticeably longer push to get the motor up & running. Pondering the schematic doesn’t suggest any reason, although maybe it has something to do with the timer motor taking longer to start with the new resistor. I hope to never know the rest of the story!

  2. #3 by steve on 2018-01-24 - 18:12

    When my Dad was in college a classmate had an internship with a white goods manufacture. One thing his friend did was defeat all the safeties on a dryer to try to start a fire. He said it was like a blow torch coming out the vent… Interestingly enough though, washing machines are blamed for more fires than dryers…

    https://www.digitaltrends.com/home/washing-machines-cause-most-fires-study-finds/

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