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Maytag MSD2556AEW Wiring Question...


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12 replies to this topic

#1 tcovenant

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Posted 20 December 2008 - 02:31 PM

Oh Great Samurai I have diligently searched your forum for answers. I have achieved fullness in 95% of my questions, but I have one left.
Background, short and sweet:
Thanks to the forum and your wisdom I have discovered a solid block of ice where the coils are. I have tested the thermoswitch and discovered that it is short when icy cold. As I warm it up in my hands, it opens (with a loud click!). It doesn't read 240K, it reads open, but as the resistor is for diagnostic purposes only this does not distress me. It is shorted when it should be.
I have ohmed the defrost coil. It reads about 30 ohms.
This would seem to indicate the ADC is faulty, yes? I agree. However:
I found a wiring diagram in the top near the ADC. It has a schematic and a wiring diagram pictorial. Very nice.
The schematic shows a WH/BLK wire going from the DEF TSTAT pin of the ADC to the point where the defrost thermostat meets the heater. It shows a red wire to the TEMP CONTROLLER, then blue to the defrost thermostat. It shows a yellow from the heater to the ADC.
In checking out this wiring, I have noticed that the WH/BLK wire disappears. Comes from the ADC to a connector, but no wire on the next harness. At the thermostat I have a YELLOW, a BLUE and a WH/BLK. Following the WH/BLK up to the connector it has no mating wire on the other side. So, essentially, there is a WH/BLK at both ends, but nothing in the middle. I was distressed.
To make things more interesting, the Pictorial Wiring Diagram shows a WH/BLK at the ADC end, connecting to nothing on the next connection. This matches what I have.
????
Why would the schematic show the WH/BLK in place, but the pictorial and actual do not?
I have no history on this fridge as I purchased it used about 3 months ago and it's been 100% fine until this weekend, when I noticed the fridge warm but the freezer cold and found your website.
I have no problem replacing the ADC, as I'm guessing it's faulty. However, is it going to work without this WH/BLK wire that's supposed to connect to the DEF TSTAT?
It's late. Tomorrow I will assemble it enough that I can jump the TEST to the L1 pins and see if anything happens (compressor shuts off and def coil gets hot, right?).
I do not know how old this fridge is. I do know that in April last year the def thermostat was replaced...there's a date of 4/17/2007 in marker on the back of the fridge and date code on the thermostat is consistent with this. The ADC has 6 pins marked DEF HTR, COMP, L2, DEF TSTAT, TEST and L1.
Another question: Did anyone ever make a schematic of this ADC controller? It's a PIC based timer with a relay. Not much else to it. The parts all check good (transistors and such), so either the relay or the PIC is faulty here.
Sorry for the long post, trying to head off questions.
The repairman says $40 to come to the house and give an estimate. $40 will buy you beer and me a DVD about house wiring! I'd rather pay you, so I hope your wisdom can provide for us both!




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#2 RegUS_PatOff

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Posted 20 December 2008 - 05:12 PM

The repairman didn't use the original Defrost Thermostat with the 240k resistor.

No problem, until you try to read the complete circuit for diagnostics.

The WH/BLK is used as a feedback to let the ADC know how long it took to defrost.

It keeps track of such things and uses that info for the next Defrost calculation.

Here's a good thread from 2005:

 http://applianceguru...forum1/119.html

If, when you short L1 to TEST, the Relay buzzes:

RegUS_Patoff wrote:

I have a Maytag MSD2756AEW and had the same defrost problem.

I drew a schematic of the ADC and found the cause and fix for the "buzzing relay"

It's a bad electrolytic capacitor, C2,  22uF @50v

Try jumpering in a good one across it. (there is a protective coating over the entire board)

Watch the polarity and also be careful, the minus (-) side of the cap is connected to L1 120v HOT side of the power line.

I drew the schematic with MS Paint, and will soon draw it  with a schematic program and upload it here. (a few messages below)

 

also, neither the compressor nor the defrost heater will work when the temp control is turned down (but the relay will still energize)  try it at max cooling setting.



 

1996 Maytag ADC Defrost Controller Schematic  ( MS Paint > pdf )

rev. 10/08/05

Attachment: MAYTAG ADC.pdf (Downloaded 342 times) Posted Image

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#3 tcovenant

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Posted 21 December 2008 - 02:12 AM

Thanks for the schematic. My C2 has some rubber stuff on one end. I work in the electronics industry, have for years. I've seen many bad caps. My C2 doesn't look bad. It's not swollen or anything. So I wonder if the rubber stuff was added on purpose...but no worries. I'll know soon enough.
The more I think about this, the more I think the WH/BLK wire should be there. There's no other way for the PIC to know if the defrost switch is open or closed and stop the defrost. Also, it can't be "adaptive" if it can't see the switch.
I did some more investigation. The repair manual I have shows the pictorial and schematic both with a WH/BLK. The pictorial that was stuck in the fridge shows no WH/BLK wire. The connectors have evidence of tool marks (did I sound like a CSI?). I think the "repairman" who fixed this in 2007 might have removed that wire.
Anyway, I'm going to go put it back together, since the 'stat and heater are good, and test this board. If it works, I'm going to run a new WH/BLK wire and see what happens.




#4 RegUS_PatOff

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Posted 21 December 2008 - 02:33 AM

Try the L1 to TEST and listen for the buzz.
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#5 tcovenant

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Posted 21 December 2008 - 06:14 AM

Well...I tried the L1 to TEST jump. Nothing. No buzz, no click, nothing.
I cut open the relay (the coil ohms good) and it looks fine. No burnt contacts or anything. I pulled the relay out and put 24V on it and it clicked. Put it back in the board and nothing. The compressor and fan continue to run, the relay doesn't click or buzz or anything.
I have checked all the diodes and all the transistors. They are fine.
I went ahead and ran the WH/BLK wire and it made no difference at all.
My conclusion is that the PIC is dead. It's not easy to troubleshoot a conformal coated board inside a fridge, so I'm not going to bother. I've checked the active components, except for the PIC, and they're all good.
In retrospect, I reckon I maybe should have checked for 120V on L1, but I did not.
I have reassembled the fridge and it is operating as we speak, though without defrost capability. I will order another ADC board.
Any idea how long I can expect to run before it frosts up again? I purchased this fridge about 3 months ago, used, and it's worked great since then...but I wonder if the defrost was already not working when I bought it...maybe that helps explain the great price I got! :?
I don't mind defrosting, now that I know what's wrong. I have a chest freezer. I'll just throw a couple of frozen chickens and milks into the fridge part, then pull the freezer stuff and leave the freezer door open for 24 hours. Hopefully I'll have a new board before that and I won't have to worry about it.
Thanks again for all the help!



#6 tcovenant

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Posted 21 December 2008 - 07:33 AM

Two more questions...

How can I tell if it's in Defrost mode with everything buttoned up and connected? The reason I ask is that I turned it on about 3 hours ago and the compressor isn't running, nor is the fan. I have a thermometer inside the fridge and it's showing a fridge temp of 50F, even though I have the fridge part set to 8. The freezer is empty, but the thermometer inside is showing 38F, with the freezer set to 5. So my thought is that maybe it went into defrost mode, thus the compressor is off.

Also, is there a waiting period before you can short the TEST to L1? In other words, I plugged the fridge in and walked around the front and shorted it. Was that OK? Should I have waited a few minutes first? I shorted it several times, too, to see if that would help...but all within maybe 2 minutes of turning it on.

Thanks!
Thomas



#7 RegUS_PatOff

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Posted 21 December 2008 - 07:59 AM

It may take a few weeks to clog the Evaporator Coils.

You could try conecting L2 to DEF HTR to see if the Defrost Heater glows.

Did the Compressor start running yet ?

Is everything connected ?

The newer ADC Boards from Maytag have a redesigned circuit  (who'd thought ?).

On those, they don't have a TEST connector, you can force Defrost Mode by cycling the Fridge temperature Control ON/OFF (3) times.

There's also a 3rd party maker of a replacement ADC board with a diagnostic LED (which you wouldn't normally be able to see) (or need to see)


Joe,

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#8 tcovenant

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Posted 21 December 2008 - 09:18 AM

I guess I should've been a bit clearer, sorry!
I started it up about 1:30PM today. The compressor was running fine. When I emailed about the compressor being off it was about 3:30.  About 30 minutes later I went and checked again and the compressor was running. Has been since, near as I can tell, though I'm not near enough to really babysit it. Have to walk across the house and listen. This makes me think, again, that the defrost cycle was on.
I was asking how to tell if it's in defrost mode because I added that wh/blk wire. That's the only change I made. If that has fixed it, I'm a happy camper! Considering the temps inside, I think it almost has to have been defrost mode...especially since it turned back on without me doing anything but opening the doors. Well, I'll give it a few weeks and see what happens.

The freezer, last check (a few mins ago) was 30F. The fridge was 48F. I seem to have icy cold air blowing down at the back-left-upper corner of the fridge. Also some coming out next to the left-side light at the top. I read somewhere here that feeling the flow isn't a good measure of how well it's working, so I'm being patient.  I'll leave it alone until tomorrow and see what happens.

I have already purchased the LED style ADC board. Should be here in a couple of weeks with Xmas time shipping. If mine is working now then I'll have a spare, I reckon. I'm actually thinking of mounting an LED somewhere that gets power when the Defrost heater is on...though I'll wait until I add the new controller board to do it.

Thomas




#9 RegUS_PatOff

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Posted 21 December 2008 - 09:40 AM

I have the MSD2756AEW

A few "problems" with that series.

The Freezer Temperaturte Control controls the operation of the Compressor and Evaporator Fan.

The Fridge Temperature Control operates a Auto (temperature) Damper Door flap
that lets the cold air circulate into the Fridge side, IF the Compressor/Evaporator Fan is running.

If the Freezer Temperature Control is satisfied,
the Compressor/Fan won't operate (no matter how long the kids leave the Fridge Door open)

Also, because the air travels through the Damper chutes, there's not much air-flow.
There is a Maytag Bulletin that refers to the MSD2756GEW and later.

Maytag Technical Bulletin

I used clear duct tape on the (6 of the 10) air-vents mentioned on the top row, and 3 more on the bottom row (far right diagram), to increase the air-flow into the fridge compartment when the Auto Damper (controls Fridge temperature) is open.
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#10 tcovenant

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Posted 22 December 2008 - 11:07 AM

Wow...super-duper thanks for that! I think that is going to make a huge difference! I operate the freezer around 20F and I have noticed some warming of the fridge compartment when the fridge is used a lot...and the compressor wasn't coming on.
I'll try the duct tape method, myself, and see how it goes.

Thomas



#11 tcovenant

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Posted 28 December 2008 - 10:47 AM

Heh...wow...so I've opened the fridge a dozen times or more since installing the wire and several times I've heard a new noise...one that I never heard before...a not happy noise. The third or so time that I heard it I realized what it is...the relay is chattering, trying to start a defrost cycle. This is very pleasing, as it means that my addition of the WH/BLK wire was needed. I've had this fridge since Sept, so for 3 months I never once heard this noise. I had no idea there was a problem until the ice built up to the point that it wouldn't cool the fridge.
So, now Xmas is over, I will be installing the new ADC board ($36 on Ebay with free shipping, and it's the LED style) on the fridge. I'm also going to see if I can mount a panel on the rear of the fridge where I can put an LED for when the defrost coil has power, and an LED to repeat the LED on the ADC board. Fun with projects, no? :)
I've also noticed that no matter how cold the freezer gets, the fridge side is at 40. No less. Open the door for 10 mins, and it will get warmer, but will cool back to 40 again, so I will be installing the tape on the correct slots.
Thanks again for everything!



#12 RegUS_PatOff

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Posted 28 December 2008 - 11:13 AM

or could you drill a hole in the Light Shield, so as to see the LED when the Fridge Door is opened ?
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#13 tcovenant

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Posted 08 May 2009 - 06:14 AM

Nah...a drilled hole is to...I don't know...hokey?
Anyway, update! It's now May. I have installed the new ADC along with the aforementioned wire. I have installed a panel on the back to repeat the ADC LED and installed an LED to tell me when the defrost heater is powered.
The thing is working deluxe! 100%!
I have the freezer set to 2, the fridge set to 4 and I get 25F on the freezer and 40F on the fridge. The milk is very tasty!
I did put the duct tape on and that made a world of difference!

Thanks again for all the help!
I've just hooked up the water lines and put a new filter. The ice-maker was playing "Sorcerer's Apprentice" until I discovered I put the wire into the wrong place. Now it works great. But someone has welded the nut on the yoke for the screw-arm and the control clip is missing...yay!
Still and all, I got a $2000 fridge for $200 plus some time and parts. I'll have the ice-maker/dispenser operating by next weekend!







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