coils freezes

[FONT=Arial][SIZE=2]Hello,

I have a 7 year old GE side by side (GSS22WGPAWW, Serial # AF 208266) Just by the sudden there is frost build up on the entire coil. After removing the freezer back panel I did the hair dryer trick to melt away the ice build up and then the fridge is running "perfectly" for about 8 - 10 days, and then the same problem: "no defrosting![/SIZE][/FONT]

[SIZE=2]If the coil is free of ice, all temps are normal (e.g. 0 – 2F in the freezer compartment and approx. 40F in the other compartment). The flap is not obstructed and works, the blower motor works also.[/SIZE][FONT=Arial][SIZE=2]
I replaced the original single heater unit to a dual unit, plus the "top" thermistor (WR55X10025 ?), but he did not change the defrost thermostat (WR50X10068 ?) neither the two others thermistors (one in the fresh food section and the other in the lower left corner of the freezer compartment).
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[FONT=Arial][SIZE=2]I ran an OHM test on the heater and the reading came in at 28 ohms, which I believe suggests that it’s not broken and I ran also the continuity test, which showed me, that this element is OK.
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[SIZE=2]I checked also the thermostat while it was "frozen" and it had continuity. I checked my seals/gasket by putting a piece of paper in between and when pulling it out, there was all around plus in all four corners of the door a “good” resistance, so seals seems to be OK too.[/SIZE]
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Any suggestions?[/SIZE][/FONT] [SIZE=2]Thanks[/SIZE].

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[SIZE=2]Christoph[/SIZE]
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Christoph,

You’ve tested and/or replaced all parts in the defrost system., so the problem is a bad main control board on the back of the refrigerator.

Here are the breakdown diagrams and http://www.appliancepartspros.com/partsearch/model.aspx?model_id=5131359

[FONT=Arial]Gene.

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