GE Frige evaporator coils freezes-up


I have a 4 year old GE side by side refrigerator. The evaporator coils freeze-up about once a month. We have to un-plug the 'fridge and let the coils thaw out for the unit tro run properly.
One other symptom, one of the two light bulbs (the upper one) in the refrigator side of the unit will not work. A new bulb will not work, the switch is good, the second bulb works.
I have a basic understanding of the system. I thawed out the coils two days ago and vacuumed out the area under the 'frige, behind the bottom grill. Where do I start the troubleshooting?
Thanx
Frank
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wrote:

If understand correctly the coils in the freezer side ice up? Maybe the automatic defrost circuit is not working? It usually comprises a timer switch, and heaters that thaw out the ice so it runs away through a drain. Many years ago our defrost timer stopped working (the little clock motor that ran it went open); cos otherwise i might have been able to repair the timer switch. It took Sears and myself a couple of weeks to bring in a replacement and myself to install it. In meantime we wired a temporary manual switch in place of the timer. Had to remember to not leave it in the defrost mode before going to bed! It's worked now for at least 15 or more years.
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That is correct.

I suspect that is the problem, but what part is brokern in the system.

The way I undestand the system, there is a mother board that controls everything, a defrost timer, and the defrost heating element. Just wondering where to start testing first with my volt/ohm meter.
thanx
Frank
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Frank from Deeeetroit wrote:

It's tough when they use fancy electronic (microprocessors or pic chips) to control a simple function. One other thing, there might be a temperature senor to turn off the defrost heater element once the coil temperature reaches thaw. This is probably to conserve energy and not put extra heat into the freezer, only to have to run the compressor to take it out later. With a simple meter you should be able to check out the heater resistance. I should be rather low, like under a few hundred ohms or even much lower. The temperature sensor, if there is one, could be open or closed depending on the design and the temperature at the time of reading. A schematic would be of tremendous help. Check the back inside of the unit, behind the panel, etc. Or, search for it on the internet.
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Art,
Thanx for the info, will check out the schematic and go from there.
Frank
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I have not read the other posts, but had a similar experience w/i the year.
I have an Amana bottom freezer.
There is a defrost timer in series with a thermostat in series with the heater element. My thermostat was bad. I had 110v to the thermostat, but 0v to the heater element when the defrost timer was on. I suppose there are many ways out there to do this, it will depend on your unit. The mfg or retailer might be able to give you the diagram.

days
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The first question, if you have electronic defrost timer, or mechanical. There are three components which frequently go bad on frost frees. The timer, the heater element, and the termination thermostat. The challenge is to figure out which one, and then replace it.
If it's a mechanical timer, it's likely in the box with the control knobs.
Heater and termination thermostat are in the freezer section, behind the back wall. You'll need a screw driver or nut driver to get the back wall off.
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