self-defrosting refridgerator freezing up ?

my self-defrosting (Fridgedair - upright and side by side) fridge is freezing up on a weekly cycle. If i defrost the **cooling coils** in the freezer manually on Monday the coils are frozen/frosted up by the following Monday... essentially blocking the cold air from going to the refridgerator side.
When i manually defrosted i measured the resistance of the heater element going around the cooling coils at 19.2 Ohms ?
What could be possible conditions to cause such a problem ?
what sort of components or actions should i be doing to repair ?
helpful advice greatly appreciated. robb
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robb wrote:

Robb,
the defrost cycle is controlled by a timer. When the timer fails the defrost cycle does not start. Your timer may have failed.
HTH, EJ in NJ
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On Thu, 16 Jul 2009 21:56:49 -0400, Ernie Willson

there is also usually a defrost thermostat that turns off the heater when the temp at the thermostat reaches a point above freezing. If the thermostat is open, the heater never gets power, and it ices up.

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robb wrote:

The heater is probably fine. The defrost timer may be bad, you may also have bad door seals that are letting in more moisture than the auto defrost can cope with.
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There should be a defrost timer which turns the compressor off at scheduled times & maybe even turns heasting coils on to speed up defrost. They are prone to failure, but cheap to replace. Mine is a black rectangle maybe 2" X 3" with a small knob sticking out to advance it manually. There may be other styles, but refrigeration places have them as does Ebay. http://shop.ebay.com/?_from=R40&_trksid=m38.l1313&_nkw=defrost+timer&_sacat=See-All-Categories
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In years past, I had to replace the "defrost timer" twice

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My guess would be a bad defrost timer. As I understand it, these are typically little timing motor bits, not all that unlike dryer timers, that operate a defrost cycle every now and again, shutting off the compressor and turning on the defrost elements for a spell.

If it's the timer, replacing it would be the obvious correct repair (and stands a good chance of being economical, to boot). Of course, if it's an old fridge, you may be money ahead in the long term to get a new, more efficient model instead, simply based upon electricity savings.
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Hi!

As others have suggested, check the defrost timer. You will likely find it at the bottom of the fridge, maybe even behind the little (mostly) decorative "vent panel". While you're at it, test the door seals. The test I've used is a dollar bill wedged between the metal and the door seal with the door shut. There should be tension when you pull on the bill. If not, you have a leaky spot in the seal.
The timer runs all the time, and you can advance it with a knob or by using a screwdriver as a test. You should be able to cycle the compressor on and off, as well as the heater. However, it's the compressor you will notice the most.
The FAQ for this group suggests failures can occur if the timer gets cold or the power goes out. Grease in the timer might harden to the point where the timer can't run or parts break.
William
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I had this happen to our fairly new Frigidaire. Element tested ok, timer motor worked. It turns out a mouse? chewed through the wire between timer motor and element. 6 or 8 wires in the bundle, only chewed through the one.
Too bad the timer didn't activate the wire while he was chewing.
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If it's the old style design, you may have a bad termination thermostat, or a bad defrost timer. What I do, is to wait till the fridge is badly frosted. Advance the timer into defrost mode, and check the amp draw of the fridge. Defrost heaters run about 5 amps. That helps you decide what parts to change.
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Defrost timer or heating elements.
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While the others are probably correct, you may need to check the fan in the freezer area to make sure it is blowing. That hapened to mine, but do not recall how long it took it to refreeze.

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are
blocking
heater
Thanks to all the responses, I appreciate your time and help.
I found the Defrost Timer under a panel inside the refridgerator and there was a manual advance access hole to advance the timer to the defrost mode.
I tried advancing the timer to defrost, the refridgerator shutdown but the defroster did not appear to turn on as you can just see it (feel it) through a vent in the back of the freezer section. It never got warm/hot and the refridgerator would turn back on after about 10-15 minutes.
I removed the timer and tested the contacts and it seemed to be functioning as expected. That is, it shift a common contact from one pole to another pole as you manually cycle the timer.
I removed the evaporator coil cover to check for power to the defroster/heater. I cycled the timer and no power.
I pulled and tested the defrost thermostat and it was not giving very good resistance readings it was bouncing all over from 300 K to 3.4 M-Ohms. ? it never really settled and that was when it was cold at 14 F or warm at 90 F
So, i guess it is a Defrost Thermostat problem.
I will order one and replace , hopefully that is the trouble.
Thanks to all for the help. robb
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Cool, figured that was the failure.
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