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Whirlpool 4388932 defrost board (Adaptive Defrost Control)

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gwakeen:
I searched the web extensively and couldn't find a wiring schematic or pin connection for the above board.  ApplianceJunk.com had several good manuals and info to download which allowed me to look at the problem in depth.   There were at least 3 or 4 applicable manuals and educational downloads that explained how the defrost feature works and showed the normal cooling as well as the defrost circuit with pins and wire colors matching what my Whirlpool had connecting to the board.  The attachment is the best of several downloads.  Note that Whirlpools original part number for my side by side refrigerator's (ED25PWXAN01) defrost circuit board is 2154958 but after looking around on the internet a while it was apparent that they have released a new part numbered 4388932. The older defrost "timers" had a timer motor on them and were crude compared to this new board which is "Adaptive".   Very interesting read, the attachment.

I had intended to jumper across the pins after I removed to board to see if the compressor and fans would start.  After removing the board I did a continuity check on the board itself and found that the relay normally closed contact....was not closed (this is the cooling circuit path, normally closed contacts).  This led to making the same check on the board itself, to see if the relay was actually that far gone (a normally closed contact would not generally fail a continuity check).  Sure enough it was actually the soldered connections on the board.   I resoldered ALL of the the Common, NO and NC pins leading to the relay.  Each circuit strip on the board connected to pins in more than one spot) This repaired the board, it works fine now.   Check by plugging the board back in and applying power via the refrigerator power cord.

However it is important to mention that the board is mechanically mounted via a plastic separator on the rear of the board that prevents close examination of the soldered connections to the board, and also of course prevents resoldering at all.   Because this plastic part is for mounting only I managed to drill several 3/8 inch holes in the plastic and expand the holes enough to allow a soldering iron to get to the pins.  This was no big deal but when drilling be careful not to push the drill into the board as it goes through the plastic mounting bracket.  There is a quarter inch of leeway, just be careful. 

This repair was on the refrigerator that came with the house, the refrigerator was manufactured in July of 1993,  Strange that those soldered connections would work flawlessly for almost 20 years and then fail.  I have had the same experience resoldering microwave circuit boards.   If you can closely examine the soldered connections you can often see what could be a defective solder joint.  These boards are "wave soldered" (placed close to a pool of molten solder and a "wave" generated that laps across the whole circuit board bottom, soldering them all at the same time).   It saves a lot of time but if one or two soldered pins going through the board are not soldered well enough it is apparent that they can eventually fail.  Another term for this is a "cold solder joint".   I have repaired TV's by arbitrarily resoldering whole areas on a printed circuit board, even without a schematic you sometimes do very well.   Because there are diodes and IC chips on the board one should reheat each joint quickly, add a little solder that has a non corrosive flux inside and get off the pin before it over heats adjacent components.  With the relay there was no worry but if resoldering in general, various areas, be careful of the heat sensitive components like diodes, transistors and IC chips.
Good Luck.

AJ:
Hi,

Great topic, glad you got it fixed!

Thanks for posting.

 :thanks:

gwakeen:
Thank you, great web site.
Jerry

jimbo6679:
Strangely enough, I have experience at a plant doing wave soldering.   It was a US company who due to the age and reduced demand for the partshad outsourced the production line to Tijuana.   It fell to me for a few months to keep this operation going.  We had all the old ancient equipment, and marginal support!     

As described, there is a large tub of molten solder, and a rotating paddle creates a wave...lets say about 1/2" height.   The board to be soldered is on a rail and passes over the wave, such that the wave kisses the botom of the board.    There are critical criteria:    proper temp of the solder, the board passes over a plate heater to be preheated.  Surface temp of the board about 170 degrees is critical and must be monitored.   Today it would be laser thermometers, but in those days we had temp. sensitve wax crayons.....you would mark with a 160, 170, and 180 crayon.   The 160 needs to definitely melt, the 180 not, and the 170 so so.       Fluxing of the board of course critical.    All of these conditions affected by board rail height, plate heater temp, speed of travel, etc.   
Anyway, the flakier the factory, the more likely to see a bad joint down the road.

gwakeen:
Very interesting  to read a detailed description of how wave soldering is actually done.  I had only heard of it, frankly that was back in the 1960's, and not really thought of how things have probably changed for the better.  As I mentioned I have had occasional instances where a resoldering worked. 

Once when operating a microwave I saw a light puff of smoke come out of the front panel and it died.  Upon taking it apart, and not knowing exactly what I was looking for, I did see one wire sticking up through a circuit board hole that had turned color a bit and had very little solder on it.   Resoldering it fixed the problem, though I had no idea of where that point was on a schematic, and no schematic to look at.  An electronics friend at work said "you were lucky" but I explained that had happened to me before and it is worth looking around to see what you can find.

Another recent situation involved a Sylvania TV that stopped working at a friend's house.   It would run 30 minutes and cut off.   She had had it for some time and it worked well.   She called a service person and they wanted to replace the circuit board for about $250 or so.  The TV only cost a bit more than that so she opted to just buy a new one.   I told her I wanted to play with the old TV so I inherited it.   I took it apart and found that the "circuit board" was quite large and was the only circuit board inside, it represented the entire TV's electronics.   I had imagined that the board the service person wanted to replace was a 3 by 5 card that was a subsystem board of some kind.  No, there was only one board and it was at least 12 by 12 maybe 12 by 18, I don't remember for sure.   I took it apart and resoldered a few connections near the incoming power cord and it started to work, after an hour I figured I had fixed it.  No such luck, it now stopped playing after about an hour and 5 minutes.   I tried soldering more around the power connections, couldn't find a schematic anywhere on the web.  Finally I used a fan to see if cooling was the problem, with a fan it worked better.  So I drilled additional vent holes in the top of the TV (it was going to be used here in the basement where it didn't matter how it looked).  That didn't help much, maybe another 10 minutes.   I found a small 6" fan at Lowes, cut a 6" hole in the side of the TV and mounted the fan.  When I turn it on now the cable box, fan and TV all come on together.   It will play all day while I watch the stock market, normally tuned to CNBC.   I have been using that TV 8 hours a day for two years now.   It took me a year and a half to get around to all of the above steps and it would still be sitting on the floor if my wife hadn't given me hell about it being taken apart and lying all around. 

I am now wondering if a Heat Pump defrost board I replaced last year could be fixed by resoldering.   It never occurred to me to try it at that time but it could work.  However that board, about 4" by 6" was replaced by an updated board about 3" by 3" so I am probably better off using the latest revised board. 

As hurricane SANDY approached our Maryland coast last week I lost the battery in my 10 year old van and the above refrigerator defrost board went out.   Talk about troubles coming in three's!!!
best to you all, Jerry

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