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ApplianceGuru.com: The Samurai Appliance Repair Forums > Do-It-Yourself Appliance Repair Help > The Kitchen Appliance Repair Forum > Magtag Wide-by-side MZD2766GEW defrost problem |
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| Moderated by: RegUS_PatOff, Pegi, appl.tech.29501 |
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| Magtag Wide-by-side MZD2766GEW defrost problem | Rate Topic |
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| Posted: Fri Aug 28th, 2009 09:50 am |
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1st Post |
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xbsun Apprentice Appliantologist, First Class
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Hi. My refrigerator (purchased in 2002) recently got the same defrost problem as discussed in many threads in this site. The evaporator coils are all frozen over. I have gone through many threads here and tried to follow the methods mentioned in them to diagnose the problem. As RegUS_PatOff mentioned in one of the threads, one of three things could be at fault: ADC, Defrost Heater or Drfrost Thermostate. I am trying to figure out which one is bad and then fix it. Below is a list thing I tried: 1. I managed to access the ADC, I shorted the L1 and Test in order to force a manual defrost cycle (as suggested in some threads). But nothing happened. I didn't hear any click sound or buzz sound. The compressor kept running. So I have no way to force the manual defrost cycle. 2. Also following a instruction from another thread, I unplug the unit and on ADC, I measured the OHMs between the red and white/black wire (bi-metal?), it's infinity (open). I also measured ohms between red and yellow wire (header?), I got about 40 ohms. Is is normal? 3.I also took the ADC board out and measured the ohm on C2, it is imfinity. (It is mentioned in other threads that ADC problem is usually caused by bad C2. My understanding is that when a capacitor is bad, its circuit will be closed so the ohm won't be infinity. Is this correct?) At this point, I don't know how to further test to determine which component is at fault. Please help. thank you. xbsun
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| Posted: Fri Aug 28th, 2009 03:57 pm |
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2nd Post |
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RegUS_PatOff Fellow, Academy of Sublime Masters of Appliantology 
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1) does the ADC have the L1 and Test pins labeled as such ? if so, try again.. if not, you may have the newer style board .. 2) The Heater, (40 ohms), could be measured between Red & Yellow IF the Cold Control is ON, and the Defrost Thermostat (Bi-Metal) is good and cold. Red & White/Black should read continuity IF the Cold Control is ON and the Defrost Thermostat (Bi-Metal) is cold. (you already measured throught it OK when measuring the Heater) 3) When this Capacitor goes bad, it opens.. it'll read infinity (may also read infinity when good) MZD2766GEW Service Manual
____________________ RegUS_PatOff http://www.youtube.com/watch?v=oPAY2LsKVEw my video production: “Easter Seals Walk With Me” (also in HQ) http://www.youtube.com/watch?v=-EBiLyYXMiA Upon leaving this Earth "Do you want the Smoking or Non-Smoking section ?" |
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| Posted: Fri Aug 28th, 2009 04:45 pm |
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3rd Post |
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denrayr Sublime Master of Appliantology 
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I remember having to turn the cold control on or off on molels with those older adc boards after shorting the pins.
____________________ RedRock Appliance Service 435-773-7838 http://www.redrockrepair.com Serving St George and Southern Utah |
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| Posted: Fri Aug 28th, 2009 05:04 pm |
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4th Post |
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RegUS_PatOff Fellow, Academy of Sublime Masters of Appliantology
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The newer ADC Boards (I don't remember when they came out) didn't have the TEST pin .. To force Defrost, no need to short any pins (difficult to access) Just cycle the Cold Control 3 times within 6 seconds and leave it on COLD.
____________________ RegUS_PatOff http://www.youtube.com/watch?v=oPAY2LsKVEw my video production: “Easter Seals Walk With Me” (also in HQ) http://www.youtube.com/watch?v=-EBiLyYXMiA Upon leaving this Earth "Do you want the Smoking or Non-Smoking section ?" |
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| Posted: Fri Aug 28th, 2009 09:31 pm |
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5th Post |
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xbsun Apprentice Appliantologist, First Class
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Thank you for the reply. My ADC board is the old one (has L1 and Test labeled on the board), it is exactly the same as in the picture in the 4th post in this thread: http://applianceguru.com/forum1/119.html I'll try again to short the L1 and Test. Does it matter if the Freezer is cold or not when I do the test? Last night when I did the test, the freezer side is still cold and the ice on the evaporator hasn't melted. Today, I have defrosted it manually. Also, people mentioned that the cold control should be placed on the max cold side. So I'll do that too. By the way, a dumb question: how do you generally short the L1 and Test? I just used a short electric wire with metal part exposed on both ends and then touch the ends to the L1 and Test. That's a right way to do that, right? If nothing happens again when I short the L1 and Test, does that mean the ADC is bad or something else is bad? Thank you again.
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| Posted: Fri Aug 28th, 2009 09:51 pm |
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6th Post |
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RegUS_PatOff Fellow, Academy of Sublime Masters of Appliantology
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xbsun wrote: ... If nothing happens again when I short the L1 and Test, does that mean the ADC is badusually ... I use the tip of an insulated screwdriver ... Make sure the Compressor is running before the test so that you'll notice if it stops. (it should) If the Defrost Terminator (bi-Metal) isn't cold, then the Compressor will still stop, but the Defrost Heater won't glow ...
____________________ RegUS_PatOff http://www.youtube.com/watch?v=oPAY2LsKVEw my video production: “Easter Seals Walk With Me” (also in HQ) http://www.youtube.com/watch?v=-EBiLyYXMiA Upon leaving this Earth "Do you want the Smoking or Non-Smoking section ?" |
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| Posted: Sat Aug 29th, 2009 06:30 pm |
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7th Post |
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xbsun Apprentice Appliantologist, First Class
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Thank you very much. I shorted the L1 and TEST with a screwdriver this time and I can hear a click sound now. But nothing happens afterwards. The compressor and the fan kept running. There's no buzz sound. I run the unit overnight to get it cold (now +10F in the freezer). I unpluged the unit (but leave the ADC board in place) and measured the ohms between various pins on the ADC board. The results are: between L1 and TEST, infinity; between L1 and DEF TSTAT: 0; between L1 and DEF HTR (20+ ohm). From my understanding, the ohms numbers sound correct -- when cold, the DEF TSTAT is closed (0 ohms). So what should I do next? I am guessing that the ADC test result above shows that the ADC board is bad (couldn't go into the test mode) but not the C2 (no buzz sound)? Would this be correct? Should I just order a new ADC board and replace it? Thanks again.
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| Posted: Sat Aug 29th, 2009 09:55 pm |
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8th Post |
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RegUS_PatOff Fellow, Academy of Sublime Masters of Appliantology
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sounds like the Relay contacts are stuck closed on the ADC Board. It maybe possible to replace the Relay (soldering, etc ..) but I'm not sure of a source for the part ... otherwise ... click on picture 
____________________ RegUS_PatOff http://www.youtube.com/watch?v=oPAY2LsKVEw my video production: “Easter Seals Walk With Me” (also in HQ) http://www.youtube.com/watch?v=-EBiLyYXMiA Upon leaving this Earth "Do you want the Smoking or Non-Smoking section ?" |
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| Posted: Sat Aug 29th, 2009 10:28 pm |
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9th Post |
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xbsun Apprentice Appliantologist, First Class
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Ok. I will order a new one and replace it. Thank you for the great help.
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| Posted: Sat Aug 29th, 2009 10:54 pm |
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10th Post |
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RegUS_PatOff Fellow, Academy of Sublime Masters of Appliantology
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RegUS_PatOff wrote: The newer ADC Boards .....
____________________ RegUS_PatOff http://www.youtube.com/watch?v=oPAY2LsKVEw my video production: “Easter Seals Walk With Me” (also in HQ) http://www.youtube.com/watch?v=-EBiLyYXMiA Upon leaving this Earth "Do you want the Smoking or Non-Smoking section ?" |
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