chad
Junior Member
Posts: 21 
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Post by chad on Apr 13, 2016 14:25:09 GMT -5
Hello. My Frigidaire Refrigerator Model LFUS2613LE1 is not defrosting. A month ago there was a power surge at our house, and consequently the refrigerator stopped defrosting. I did some diagnosing with a multi-meter, and determined that the Frigidaire Refrigerator Main Control Board 242053503 needed to be replaced. (The defrost thermostat has voltage when not engaged, then tests 0.00v when engaged, and the defrost heating element has resistance, so I assumed it's ok). The temperature control board was also replaced due to my error (bridged the wrong wires trying to test the evaporator fan, and created a short on the circuit board). After replacing both circuit boards the refrigerator still does not self-defrost. I then re-tested the defrost components; the thermostat still changes voltage when engaged, and the voltage in the wires that connects to the heating element changes along with the thermostat. When the thermostat is not engaged, the heating element feeding wires read 12v, when the thermostat is engaged, they read 2v. Is this right? It would seem like they should be 2v or 0.00v when the thermostat is off, then the 12v when on? Also when testing: the heating element has resistance, but does not show the same voltage when I put the test probes on the element's connectors. The element's connectors show 0.00v, even when the feeding connectors are 2v or 12v. I thought that meant the element was bad, so I purchased a "tested, working" used element on Ebay. The new/used element shows the same multi-meter results, and no heating. i'm not sure what to test next, and not sure if the elements are working or if the no-defrost problem if from a different source.
Any help is appreciated!
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Post by Casethecorvetteman on Apr 15, 2016 23:19:36 GMT -5
What is between the element connections and where youre seeing the voltage? You need to test the continuity between these connections.
Take a reading of the element with it disconnected.
It sounds to me like there is a break in a connecting wire from the supply to the element.
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chad
Junior Member
Posts: 21
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Post by chad on Apr 17, 2016 10:23:32 GMT -5
I tested the voltage at the feeding wires that attach to the element wires (with the element disconnected from the feeding wires). If I test voltage with the element wires connected, I get a 0.00 reading. (See 1st picture)  If I disconnect 1 or both feeding wires, I get 2v when the thermostat is engaged (see 2nd picture), or 12v when the thermostat is not engaged.  The element Ohm reading, with it disconnected, is 29.2. I found someone with similar symptoms here: www.shopyourway.com/questions/1191076 |
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Post by mastertech on Apr 17, 2016 21:44:47 GMT -5
Have you located the defrost thermostat?
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Post by Casethecorvetteman on Apr 18, 2016 2:17:13 GMT -5
The element is fine.
The thermostat has very limited control over the defrost heater, there will be some sort of mechanical timer or electronic control for the element, which should be fed a lot more than 12v. Itll take a lot more than 5 watts to melt that ice, so you can disregard the 12v and 2v readings.
It should be mains voltage feeding that element, so you need to track the wires back til you either find a defrost timer or a relay on a circuit board and do further tests. If you choose to continue, then i would advise you to be VERY careful around mains conductors, its very dangerous.
Im not familiar with that model and have not seen that brand sold here for a long time, and not knowing where youre located makes it a little more difficult because i dont know what mains voltage youre on there either, or you best methods of testing.
If youre in a country that has the MEN electrical supply system, all tests on AC devices that have their conductive surfaces earthed should be made active-earth ( should read around the mains nominal supply ) , then neutral to earth ( should read very close to 0v AC ) If youre not, then testing active-neutral is acceptable, but can give misleading results.
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chad
Junior Member
Posts: 21
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Post by chad on Apr 19, 2016 8:43:18 GMT -5
I have locate the defrost thermostat, and it turns on and off to correspond with the temperature. I will trace the wires from the element, and see where the 120V should be coming from.
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Post by Casethecorvetteman on Apr 19, 2016 9:36:41 GMT -5
Yeah the thermostat does that job and only that job, i would expect there would be a relay or defrost timer for that element and there may be auxilary contacts feeding the thermostat so cooling does not operate during defrost, but they are not all the same.
There will be some form of interlock between the defrost and the thermostat to prevent both operating together, but at this point we need to establish what is feeding the defrost element.
The defrost cycle does not simply kick in when the cabinet reaches the set temperature, it will be set to defrost at timed intervals. If this is done with a mechanical timer, it may have stopped turning, or the contacts could be burnt out. If it is electronically controlled, there will be a relay that pulls in for defrost, and if it is getting it's signal and not operating, the coil may be burnt out or the contacts could be burnt out.
Can you get a picture of the whole control circuit?
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Post by Casethecorvetteman on Apr 19, 2016 9:52:29 GMT -5
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Post by mastertech on Apr 19, 2016 10:33:45 GMT -5
Test the resistor that is circled in red. I think it should be 220 ohm.  |
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chad
Junior Member
Posts: 21
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Post by chad on Apr 20, 2016 15:28:17 GMT -5
The resistor tests 10 ohms.
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chad
Junior Member
Posts: 21
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Post by chad on Apr 20, 2016 15:36:09 GMT -5
I know the thermostat reads 0.00v when on, and has a higher reading when not engaged, but I can't remember the "off" voltage. Is there a way to test the 4 relays on the control board?
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Post by mastertech on Apr 20, 2016 20:48:56 GMT -5
How are you testing the defrost thermostat?
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chad
Junior Member
Posts: 21
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Post by chad on Apr 21, 2016 8:13:53 GMT -5
I leave the multi meter testing probes on the wires of the thermostat (I've taken a piece of the wire covering off to expose the wires). Then I've defrosted the coils and have seen the multi meter show a different reading on the thermostat for cold vs warm.
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Post by mastertech on Apr 21, 2016 8:31:18 GMT -5
And is that thermostat wired in series with the heating element at the evaporator?
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chad
Junior Member
Posts: 21
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Post by chad on Apr 21, 2016 10:59:56 GMT -5
Yes it is. The thermostat is plugged in while I test it.
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