Sears dehumidifer problems

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[I've cross posted this to what seemed to be the most appropriate places; no flames please]
I have a 4-year old Kenmore 65-pint dehumidifer which sits in a basement room containing electronics, etc. and I keep the relative humidity below 50%. It has functioned well until I turned it on for this summer season (in the winter, hot air from the furnace keeps the room dry as a bone). Nothing has changed in the room, or the basement, which would affect the ease with which humidity could leak back into the room.
I keep a digital thermometer/hygrometer in the room (double-checked for accuracy with another unit elsewhere in the house). The problem seems to be the (digital) humidistat (which has a range of 40 - 60%) which now seems to be about 10 - 15% too high. As a result, even with the dehumidifer set at 40%, the steady-state humidity in the room barely goes below 50%.
I checked the warranty and it only applies to the sealed components (condenser, compressor, etc) so I opened the unit and found no evidence of a humidistat adjustment or trimmer. The humidity sensor is mounted on the inner frame of the unit, within the stream of air flow between back to front, next to the sides of the coils. When it has stopped running at an ambient humidity of 50% (even though set to 40%) it restarts again when I blow moist air from my mouth at the sensor.
It looks to be sourced from LG, and browsing in stores I see newer units which allow set points down to 30% relative humidity, as well as low temperature operation. I'm toying with the idea of simply replacing the unit, but wonder if it's worth the expense of having a non-warranty failure repaired - or the hassle of ordering a replacement sensor and trying it myself.
Any thoughts?
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My first thought is to rewire the unit with a remote humidstat. The control really does not work all that well mounted internally. Its kind of like a feedback system, since water collected in the unit, evaporates and affects the internal humidstat. I don't know whats more cost effective as far a solutions. Try replacing the sensor???
greg
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I thought of the placement of the sensor itself; however, I wonder about its viability since this _used_ to work relatively accurately, and the room and the basement it's in have not changed.
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It may not work right but you dont need the humidity that low.
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The fault can be the humidity sensor, control board, or that the cooling is a little weak due to some of the gas leaking out (bad seals), or the lack of proper pressure from the condensor.
The service rep for your machine can test for the faults, and service them. If you have an extended warrenty, this should all be covered.
Jerry G. =====
Mike S. wrote:

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A couple tests to determine if it is a sensor problem or a loss of coolant (which may be under your warranty) would be
1. After it's been running for a 15 minutes or so, are the evaporator coils (the cold ones) more or less uniformly cold without ice? If they are, then the sealed system is working fine. If only part of the coil is cold and/or there is ice, then it's low on coolant.
2. If you set the humidistat at 50 percent, does it maintain 50 percent, or would it then be around 60 percent? In the latter case, it's a sensor problem.
--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html
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Given their cost of a new unit and the rip off sears service price your much better off replacing the unit
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Heck, and I always thought this was a repair newsgroup. Seras isn't the only option for repair.
--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html
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I looked up the unit in the parts database and found that I can order a replacement sensor assembly for $21. I will replace that first, and if there is still a coolant issue once the humidistat issue is resolved, will bring it in for warranty service (since the warranty only covers the sealed coolant assembly).
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snipped-for-privacy@xinap.moc (Mike S.) writes:

Sounds like a plan. But do take another look at the humidistat. There may be some magic screw you have overlooked.
It's quite possible for these things to shift calibration. It's probably just a strip of a plastic-like material (used to be human hair but I don't think they use that anymore!) that changes length depending on humidity.
--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html
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The humidity setting is via a digital touch panel in front. I don't see any way to tweak the adjustment as the sensor assembly is simply attached by a long cable to the back of the PC board on the control panel.
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snipped-for-privacy@xinap.moc (Mike S.) writes:

What's in the sensor assembly? If it changes resistance or something like that perhaps it could be faked out.
--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html
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I haven't removed or opened it. It's a small white box with a grating in front, sort of looks like those little piezo sound transducers. Has a 3-pin connector on the bottom. Will look more closely when I open the case to install the replacement.
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Mike-
After setting, does the touch panel read out its version of actual humidity? If it only shows the set point, you don't know whether it is shutting off because it has reached the set point, or because the compressor has shut down from an over-current condition.
It might just be a coincidence that the cycling compressor appears to maintain a particular humidity level.
Fred
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It only displays the chosen set point; not the actual humidity.

Hmmm. in any case, I'm replacing the sensor, so it should eliminate that variable.
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Sam Goldwasser wrote:

somone suggested taking it in for service they charge so much thats a loser. I repair machines for a living but some new stuff today is so cheap and parts so expensive if available at all your just better off replacing it:(
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Hi!

Wow...I never heard of one using hair as a humidity indicator!
This must not have been done in a long time, as I've got a Sears Coldspot dehumidifier that's at least 30 years old and it uses a conventional thin layer of plastic in the humidistat.
William
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OK. After running a few minutes, the center coils are definitely cooler than the ones towards the top and bottom of the evaporator.

The unit consistently maintains a steady-state humidity 10 - 15% higher than the set point.
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If the unit shuts off, they you still have reserve capacity. I have one unit I have had for many years. It just started to show signs of loosing freon. The last parts of the coil starts freezing. Its still working though. Watching the moisture build up on the coils will show if its basically working.
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snipped-for-privacy@pitt.edu (GregS) writes:

Good point:
3. If unit shuts off without reaching humidity set-point, not a cooling problem.
--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html
Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.
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