What is keeping this KitchenAid dryer from stopping on the auto setting? -PICS and info included-

[stephenk]

This is a Kitchen Aid electric dryer model KEYS850GQ0. This is a basic Whirlpool-made dryer that has been produced for years and Whirlpool still make this same basic model under various brands.

In the last week the dryer won’t stop on the auto dry cycle. It will just run after the clothes are dry and keep going. It seems to work normally on timed settings where you just set a certain number of minutes.

Read below and feel free to offer any suggestions or poke holes in my logic. I’m a competent DIY’er with plenty of tools, so I’m not afraid to tear into this if it’s a cheap fix. So far, I’ve disassembled and cleaned a whole bunch of things. We will see if that helps.

I may just replace the dryer with a new one if it’s not easily fixable. I bought this used for $125 in 2008, so it has served me well and I’ve definitely gotten my money’s worth. The only repair it needed over those years was a faulty thermal fuse that I diagnosed and fixed myself.

I’ve done some research and I think this auto dry function works:
-The wet clothes hit the sensor in the tub and make a complete circuit. When they’re dry, the circuit is broken and that starts a final countdown on the timer.
-Basically, when the clothes are wet they provide a ground path and when they’re dry the circuit it broken and that allows the timer to advance and eventually end the cycle.

Here’s what I’ve checked:
-I took out the moisture sensor and it appears fine. This is a pretty simple device. The way it operates, the only malfunction I can think of is if there’s a crack or something that allows the sensor to constantly ground out and not trip the timer to end the cycle when the clothes are dry.
-The circuit board looks OK. one side is a little brown with age, but nothing is obviously burned or blown up. I don’t know of any definitive ways to test it.
-No wires are obviously cracked or broken.

Here are my suspicions:
-Either the circuit board or the timer have failed.
-If the circuit board failed it wouldn’t tell the timer to move towards the end cycle when the moisture sensor detects the clothes are dry. But, I have no way to check this and I don’t know if the dryer would run at all if the circuit board failed.
-If the timer failed, perhaps it wouldn’t advance to the end of the cycle when the moisture sensor indicates the clothes are dry.

 

[stephenk]

Here's a close-up look at how the sensor mounts and the sensor itself. The plastic bushing that insulates the sensor from grounding is intact and the sensor itself looks fine.

 

[stephenk]

The circuit board looks OK, but as I mentioned before I don't know how to specifically test it with my multimeter.

 

[eronie]

Sensor

The back of the sensor strips looks shorted to me. Test it with your multimeter, should read infinity. Wet clothes competes the circuit between the two bars causing the board to time out. When sensor bars no longer are shorted out from wet clothes bord sends power to timer motor thus ending cycle.

 

[combo52]

Hi,Try pulling the yellow-red off the sensor and see if the dryers timer advances in Auto-Dry, if so the sensor is shorted, if not its is likley either the timer or the circuit board, the timer is fairly easy to test with an ohm meter, if it is OK look for a deal on a new or used CB, the dryer is diffidently worth keeping unless you have the option of converting to natural gas.

 

[eronie]

Timer is ok as it works with timed dry.
Sensor strips are shorted, probably due to fabric softener. Soak sensor in alcohol and scrub with toothbrush, dry,should be good to go. Should read infinity with multimeter.

 

[stephenk]

The sensor strips are not shorted that I can see. We don't use fabric softener and the sensor tests fine with my multi meter. There's no continuity between the strips, which is the way it should be.

I don't see the claimed short that you say you're seeing.

 

[stephenk]

There's also infinate resistance, as it should be.

There was some link and junk under it when I pulled it off, by it didn't look like anything that would cause a short. I cleaned it out. I'll put it back together and see if the situation is improved.

 

[stephenk]

I cleaned up the sensor, cleaned out a couple other things and cleaned up a ground for the circuit board that was rusty.

I put it back together and I can hear the timer ticking on auto when no wet clothes are touching the sensor. That seems like a good sign, but I'm running it now to see if it actually advances the timer on the auto setting.

Thanks for the suggestions so far.

 

[eronie]

Gunk under sensor

 

[stephenk]

I can offer an update. I've continued to have some intermittent problems with the timer, including on other settings. Looks like it's the timer itself that most likely is the problem