Intermittent problem with Kenmore Dryer Model #110.63952101

[storm]

I was just able to observe the problem, finally, under timed dry operation. I had the timer set for 40 min, cotton/towel high heat setting. At 30min left on timer, the dryer stopped with 3 beeps. I pressed the push to start button and the dryer just beeped 3 times and would not resume cycle. The timer does continue to count down, but the dryer was already stopped. This suggests , according to the tech sheet, a problem with the thermistor, or the harness connecting the thermistor to the even heat board. I think we're finally getting somewhere, as the thermistor appears to come into play during auto dry as well. Do you agree? I will check the connections from the moisture sensor as well, but am unsure how it comes into play during timed dry.

[Samurai Appliance Repair Man]

Ahh, this is making much more sense. Earlier you reported that the timer was counting down too fast. That's what led me down the trail of the timer and the even heat board. It sounds like you're saying that the timer is doing it's thing correctly, but the motor stops running prematurely. Do I have it right?

The thermistor should only be involved with the heating circuit, not the motor circuit-- refer to the strip charts on page 3 of your tech sheet.

Have you done the Damp Dry Test called out on pg. 1?

Repeat the same test but with the no heat option selected. If you can't ever get the failure to repeat in no-heat mode, then it's time to do the moisture sensor and thermistor tests called out on Page 8 of your tech sheet.

[storm]

The damp dry test passed fine. Moisture sensor test passes.I checked the continuity of harness, appears fine. Hooked up meter across thermistor to monitor voltage drop during operation and noticed a big increase (doubled) after about 10 minutes, then dryer would stop. Checked resistance across as soon as possible and seemed very high, 200 - 300k. checked out of circuit and would be closer to normal.  Tightened connectors (crimped with needlenose) at thermistor and ensured connector at board was seated tight and all wires were pushed into connector good. Have been running dryer with meter attached for awhile now with no failure, but I'm not calling it a success yet. Thought the thermistor was failing after heating up, but it seems, at this point, that the connections may have gotten resistive due to vibration, causing erratic input to the Control bd. Only time will tell, I guess.

[Samurai Appliance Repair Man]

The thermistor is a silicon device and, as such, can act very squirrelly in its dying stages.  I have seen thermistors in other applications behave strangely just before dying altogether, temporarily throwing me off the track.  What indication did you have that the thermistor might be flaking out on you?  They're inexpensive so I'd say if you have any doubts about it, it's worth replacing it just for good measure.

[storm]

Just a hunch due to the fact that the control bd didn't fix the problem and I figured the correct operation of the timer, at least during auto-dry, seemed to be dependent on the input from the thermistor, as it controlled the heat relay. I was using the theory of operation from the older system using thermostats, but figured it couldn't be a whole lot different. I, unfortunately, did not observe the true nature of the timed cycle failure until tonight, because I would listen for the beep signaling the end of the cycle and the timer was already advanced to off by the time I got there. When the timer didn't fix the problem, I was frustated enough to look back at things I had already dismissed. The thermistor tested fine when I measured it static and cold, I never saw the 3-beep PTS failure because I never tried it at the moment of failure, like tonight ,the moisture sensor tests passed, etc. I also surmised that the control bd had to be the problem, at first, because the problem occurred during both types of cycles. I agree that the thermistor is inexpensive enough that I will be replacing it just so that I don't piss my wife off any more than I already have.  It's been quite a learning experience, though!

[Samurai Appliance Repair Man]

[user=701]storm[/user] wrote:

It's been quite a learning experience, though!

For both of us!  This will be an interesting one to see through to its successful conclusion.  :hiking:

[kdog]

wonder what the conclusion was ??? probably a wire off the sensor bar or sumpin like dat.. :shock:

[storm]

There were no wires off any components, but I did tighten all slip-on connectors. The connector on the even-heat board for the thermistor and moisture sensor was not snapping into place and staying on firmly so it could have been intermittently losing it's good connection due to vibration since it hangs downward when the panel is in place. I just bent the tab out to correct that. I'm still not sure if the dryer is permanently fixed and I still plan to replace the thermistor as a precaution since it doesn't cost a great deal and could potentially be breaking down during continued operation. My wife claims the timer cycles are taking too long to dry the clothes (she tried it once), but the auto-sense cycles seem to be working just fine. That would be a different problem than I previously was dealing with so I'll approach it when I'm convinced there really is a problem and not just a paranoid operator!

[Samurai Appliance Repair Man]

Long drying times are usually a sign of a restricted or overly long vent:

http://fixitnow.com/2003/10/appliance-tip-of-day-ultimate-dryer.htm