Troubleshooting Help needed with electronic sensor; Kenmore HD Soft Heat 'Ultra Fabric Care' Dryer.

[turbokinetic]

Hi folks. I'm helping my mom solve some minor troubles around the house. One of the issues is her dryer will not time out and stop, when in the "automatic" cycle. If the timer is rotated to the "timed" cycle, the timer will always correctly time out and shut down the dryer.

In looking at the schematic (sorry I didn't take a picture of it yet) there is an electronic sensor board which will pause the timer motor in the automatic cycle, as long as there is moisture remaining in the clothes in the dryer. The circuit has a pair of electrodes which contact the tumbling clothes in the drum and apparently detect the conductivity of the moisture.

This is not working and is never energizing the timer motor when in the automatic mode.

The board looks to be simple and made of discrete components which I could theoretically test one by one looking for any which don't match their markings. But I thought I would ask here first; if anyone has a troubleshooting guide for this dryer.

While I had it apart, I cleaned out all the lint, re-oiled all the rollers, the belt idler, and the motor's oil felts. Then put in a new belt. It runs a lot quieter for sure! Now to get the automatic sensor working. The model info follows.

Kenmore Heavy Duty Soft Heat "Ultra Fabric Care" dryer
Mod: 110 86681800 66818
S/N: M74663455

Thanks sincerely in advance for any advice!
David

 

[sfh074]

Dryness board ....

David,

I cross referenced the model number and found the part number for the board, #61236.

Ebay has 7 of them at the moment and the board has several cross ref numbers to look under as listed on a few ebay listings:

https://www.ebay.com/i/123739953393

Bud - Atlanta

Sorry to hear about your father.

 

[turbokinetic]

Thanks

Hi Bud. Thanks for the info from the eBay board. Also, thanks for thinking of me and my mom after losing dad this week. I know we'll get through this but it is going to be a very hard road for a while.

 

[spacepig]

David,

Unfortunately I can't help with your mom's dryer, but I wanted to say that I'm sorry to hear about your dad passing away. It's hard losing a parent :-(

Jeannine

 

[turquoisedude]

David, my deepest condolences - I was saddened to hear of your father's passing.  

 

[turbokinetic]

Jeannine, and Paul - thank you for the condolences on my father. Mom and I are trying to get through Thanksgiving today and it is very difficult.

I took the board back out of the dryer and used a megger to see if there was any sort of conductive dirt on the sensing probes. I was able to get a reading of 2.2GΩ at 1000V test voltage. That basically means the probes are very clean and dry.

 

Will be ordering that board. Also trying to reverse engineer the old one and determine which components went bad on it.

 

 

[kenmoreman]

Sensor board replacement

One unique characteristic of this electronic drying sensor is that the timer motor runs on 80 to 85 V as opposed to 120. You need to be careful if applying voltage directly to the timer motor because you can burn it out.. I don’t know if any other timer motors that had this characteristic but they may be more out there on different electronica systems.

 

[turbokinetic]

Thanks for the info. Yeah, I had noticed that the timer motor is powered through a 750Ω resistor on the board. In looking at the timer motor, it is clearly marked "120V" on the motor casing its self. When the timer is running in the "timed" (not automatic) mode, the resistor is dropping about 15V with the timer motor getting about 105V.

As far as I know, the timer motor has never been replaced since our family has owned this dryer, which has been more than 25 years. It has never had an issue until now. Had it not been for this fact, I would wonder if the timer motor was possibly an incorrect part.

Do you know how many different variations there are to the board? I am trying to identify the component "Q1" on the board, which may be the cause of the problem. It is likely a triac but the numbers don't seem to cross.

I want to try to develop a repair process for this since eventually there will be no more NOS or used/good boards available.

In the pictures I have drawn a diagram which represents the PCB circuit. All the components are relatively easy to identify (and therefore test) except the semiconductor device Q1.

Sincerely,
David

 

[combo52]

Q1

Is a triac, I would try replacing it and see if that fixes the board, WP used a lot of traics on their boards for their early electronic washers around this time.

 

John L.

 

[turbokinetic]

Hi John. Thanks for the pointer. I have some triacs which are heavier parts. Will swap one in and see what sort of action I get.

 

[turbokinetic]

Follow-up....

Due to some time constraints, I went ahead and ordered the used dryness board from eBay. Installed it and the dryer automatic mode is working well! If I have time in the future, I will replace the TRIAC on the original and see if that was the only issue. Thanks again for your help!

 

[repairguy]

Congrats on keeping the vintage Kenmore going!

 

[sfh074]

Yeah ....

It's either the triac or the zener diode. Glad you got it back running!

Bud - Atlanta

 

[turbokinetic]

Bud, I hope to have time to check the old one out soon. Will report back for sure!