American Fridge problems, work down so far and advise sought

[deema]

So, I’m originally from Yorkshire, and all the jokes about us Tykes being a Scotsman with all the generosity squeezed out, spilt a current in two, short arms and deep pockets are I’m delighted to say all true!
With my proud heritage of make do and mend my challenge has been to resolve the family American fridge that has been misbehaving. Working on the principle that if it’s broken, I can’t break it any further I’ve started on a journey of learning and fixing. Now, I was a life time ago a graduate electronic engineer, and I have to say some of what I’ve done I should score as Z minus as on reflection it was obviously wrong. Anyway, thought Id share what I’ve learned as it may help someone else.

The fridge is a Samsung, ancient like me! The problem has been that the fridge was displaying it was at 3 degrees, however there was a large temperature variant from the top to bottom of the fridge, with the top warming up to circa 15 degree…….good environment for all those bad bugs to have a field day,
The freezer was working fine, and the cold water dispenser was sort of cool but no longer cool.

So, initial thoughts are that the refrigerant is OK, not leaked out, the compressor must also be working as the freezer is still nicely frozen down.

This is the fridge, after I’ve just finished tinkering with it (Round 4, 3 wins to the fridge so far!)

I’ve so far, had three earlier attempts to fix the problem, hence if anyone can spot anything I’ve missed then please shout up.

The inside of the fridge with all the shelves etc removed looks like this.

It consists of the water dispenser reservoir at the bottom, and the two panels which are both screwed and clipped to the body of the fridge. All really easy to remove.

The problem is that the expansion coil is freezing up and the auto defrost system isn’t working.
I believe the fridge and freezer work as follows.
The expansion radiator (well it’s what I’m calling it) is located behind an insulated panel. The compressor pumps when ever the fridge or freezer asks for cooling which feeds both the freezer and the fridge at the same time. A fan on either side then pulls air around the expansion radiator and pumps the cooled air into the top of the fridge / freezer where it then settles back down to the bottom causing a circulation and a constant temperature throughout the unit.

The following photo is the back of the lower panel I removed. It has a fan screwed onto it marked in Red. Just below the fan marked in blue is where the air is drawn in from around the expansion radiator befire being blown out of the top, through the top panel which has vents along its length to let the chilled air into the fridge.

So, the first job was to defrost the unit. Hair dryer came in handy. Next locate the PCB which is in the base of the unit around the back and check the continuity of the circuits. The fridge has two RCDs (Resistance Temperature Devices) to detect the temperature. One located in the upper panel which I’m guessing is what causes the fridge to turn on and off the demand for chilled air, and another located in the top left hand side of the radiator, to I think this regulates the auto defrost cycle.
Autodefrost is I believe achieved by heaters switching on and warming up the area which is insulated from the main fridge / freezer. The fan isn’t on at this time, and as a consequence the main fridge remains cool and is virtually unaffected. After a preset time or once a certain temperature is reached the auto defrost cycle stops and the refrigerator starts up again. Well, that’s my theory!

So, dumb mistake number 1, the obvious is almost always obviously wrong, a mantra I’ve lived by but broke. I found that everything when tested from the PCB connections seemed fine, but I did find that the relay on the PCB for turning on the heaters had failed. So, eBay being my friend a new relay was soon in my hand and a quick soldering job I hoped fixed the job. Sorry no photos of that.
Nope, after a week the fridge was back misbehaving. I don’t have a manual for the unit, and couldn’t find anything online, so a bit of intuition was required. I read that the heaters should be around 700 ohm, and I was reading 2.5K ohm. Strange, heaters normally only fail open or short circuit….dumb error no 2. However, the back of the fridge had a sticker indicating that there are three heaters in the fridge ….weired!

Anyway, the hunt for the heaters began. I only found what I believed as a heater at the bottom of the fridge. A type of heater mat stuck to a plate. It’s located here, the thing with a hole in it.

 

[deema]

The heater had a resistance or 2.5K ohm. Bingo! So I bought a new one. I suspected there were two heaters in one, and one side had failed.

Replacing it is easy. Peel of the old one, and the new one had a sticky backing. I made an educated guess on what I needed as I assumed if it wasnt quite the right size I’d make it fit! Well it fitted perfectly…….however…..it too had a resistance of 2.5K ohm. Darn! Let’s try it anyway. A week later, bad news still not fixed.
So after a lot of looking at what was staring me in the face, I did what any sensible person should have done initially……follow the wires. What I found was that what I believed was just an expansion radiator wasn’t. It was actually two things clipped together. The actual expansion radiator and a heater……that looked identical. This is what the two look like as a unit.

I’m making myself feel better that it looks like just a radiator to me! measured the resitrance of the newly discovered heater it was infinite, or open circuit, so definitely faulty. Off to eBay again and within a couple of days I had this.

Again a bit of guess work, but it is actually the right unit…..or at least it fits perfectly. The heater is clipped on, it takes a bit of patience to get it off as you don’t want to disturb the radiator behind and fracture the pipes and let out the refrigerant. You just bend away the clips with small pliers.

This is with the heater removed.

The new heater element about to be installed, excuse my bandaged finger……hedge cutter love bite!

Close up of the clips for the heater.

So, the resistance of the new heater is where I thought it would be, so everything seems good. The third heater which I’ve never found is supposed to heat the water inlet to the chilled water reservoir I believe. Anyway. I have my fingers crossed it’s now up and running.

If I have now fixed it……please shout if I’ve missed anything ……and a week or so will let me know……it was actually a quick and very cheap fix and stopping a perfectly good fridge becoming landfill.

I just wish I knew the front panel button combination of buttons to press to put it into defrost mode so I could have checked it was now all working. I have checked the freezer and it’s defrost system which is identical is working so I’m assuming the brains on the PCB are OK.

 

[John Brown]

Apologies for the fact that I haven't thoroughly read your post, but I have an attention span problem.
However, we used to have a Samsung fridge freezer if a similar appearance at our tennis club, at which I was the volunteer bar chair. Two or three times, over the years, the fridge side stopped cooling properly, and I found that turning it off and leaving the doors open for a day or two, seemed to sort it out. It seemed that there was no cooling as such on the fridge side, but cold air was blown in from the freezer side. Sometimes, especially when people had brought items along for special events, and placed them at the back of the fridge in plastic bags, the airflow seemed to become blocked, and the duct between freezer and fridge would be blocked with ice. Leaving the fridge off with the doors open for a couple of days seemed to fix it.

 

[Argus]

The 'expansion radiator' is termed the 'Evaporator' because that is what happens to the liquid refrigerant when it enters, past the metering device (usually a capillary tube) - it evaporates.

These American fridge things are complexity crammed into a small space, but the basic process is simple. If you have only one compressor (the black round thing at the back - often called a 'Pot' or in some areas a 'Dome') then the whole thing is one continuous refrigerant circuit; if there are two, the there will be two circuits - one for the higher temperature operation, the other doing the lower. From what you describe, it sounds like a single system.

You don't mention which refrigerant is used; that's academic because, apart from all the legal stuff about handling it, you'll need a lot of specialised and expensive kit. But it would be interesting to see which one was used; it will be identified as a number on the machine's name plate.
Look for a letter R, followed by a number or set of letters and a weight in grams. It's probably R 134a.
It's unlikely that there's a leak. They contain a relatively small, but critical weight of gas and small fugitive leaks are very rare. If there is one it will run continuously on a vacuum, doing nothing.

So, it was most likely a kaputten defrost heater....... the ice build up blocked the air-flow through the fan section and stopped the air flow, thereby increasing the ice build up..... Also, there may be a filter in it by the fan.... worth checking, also that the external heat-exchanger (the 'condenser' - because the hot gas condenses there) is clean.

Hopefully it works for you........ well done for perseverance. Thirty years ago you'd have got a job in my firm - refrigeration engineers were extremely well paid in those days.

 

[clogs]

same dam problem with my Samsung....
it was a full size yank fridg/frzr.....
I changed all the sencers etc....
just got fed up with it in the end.....oh and the ice cube maker quit within warranty but being France there's no actual warranty......
anyway......
SO, once the fridge started to warm up a little.....butter was our go to gauge....
we just emptied the thing and left a floor standing fan run for at least 2 hours to defrost the freezer side of things....
we got another 6 years out of the fridge like this.....
left it in the house when we sold up....telling the new owners it's little foilbles....

all our friends had yanky fr/freezers but dif makes...none of them had the same prob...
So, sorry wont buy another Samsung freezer again....

 

[deema]

Thanks Argus,
Its a single Pot system, but I couldn’t find a label. The fridge is around 17 years old, and I can see where a label used to be on the POT. I had cleaned the external heat exchanger of the accumulated crud. Before embarking I’d checked that the freezer was getting down to minus 18 to try and ensure it wasn’t a refrigerant leaking issue……that would be the death nail for it.

I’ve taken the fan out after your advise, no filter, but a little ice in the compartmeant.

 

[Argus]

I thought that it was a single system from your description.

The info label in question will be the one with the model/serial numbers, electrical data etc. usually - but not always - somewhere inside the cabinet where it can be seen, rather than buried in the back. The 'R' number will be buried in there somewhere. In general, compressors will run on a variety of gasses, so the specified refrigerant is unlikely to be on that.

The defrost period initiation will be controlled by a combination of time and temperature. The best non-invasive check is to run the thing empty from room temperature for 24 hours during the pull-down period, before the automatic defrost is initiated. After a few hours, and at intervals, visually examine the various evaporator assemblies as a whole. They will, most likely be piped up in series.

You need to look for an even frost build up on the all pipes from the start (where there may be a set of capillary tubes, to the end of the last part in the circuit. This will likely have a large bulge in the assembly - an accumulator, designed to catch any un-evaporated liquid at the end of the process.

Ignore cabinet temperatures at this point - look for a nice even coating of frost right through - or stopping just short.

 

[Sandyn]

So, I’m originally from Yorkshire, and all the jokes about us Tykes being a Scotsman with all the generosity squeezed out, spilt a current in two, short arms and deep pockets are I’m delighted to say all true!

Brilliant write--up. I've got a very similar problem so, being Scottish, I'm delighted you probably saved me a bit of cash buying the wrong parts.

 

[deema]

This is the only label with the part number on it, there are no other labels on the fridge. It’s what gave me the pseudo wiring diagram

 

[deema]

I have found photos of the PCB. It’s a fairly simple circuit, and you can see by the through hole components the age of it. The majority, if not all of these will be surface mount these days.

The black and white boxes at the bottom of the pictures are the various relays that switched on and off things like the heaters, fan and ice making bits and pieces. They are just a switch that is actuated when 12 volts is applied across two pins, allowing mains voltage to be switched on and off.

Luckily the designer added proper notes on the PCB to identify which relay did what so identifying the relay to test was very easy. These are the replacements I bought off ebay.

 

[GuitardoctorW7]

As a safety measure I'd change all the electrolytic caps. 17 years is a long life for them.

 

[julianf]

we have, i think, the same fridge.

i had to use one of those "kits" on it to replace various bits some years back

currently the freezer temperature is no longer displayed or adjustable, but as its correct, i leave it be...

Ill read through your thread later, but...

The unit was a recall unit that needed a mod. If yours has not has the mod done, then they will fix any other faults when the recall chap (not actually a recall, but a mod) comes round to fit the mod.

You might like to look into that?

 

[deema]

Thanks Julianf, if you have any further details of the recall that would be appreciated. I’ve tried google, and nothing seems to come up, but that might me my poor search skills.

 

[DRC]

We have a Samsung almost identical to yours and it's now 16 years old. I used to be a Tech troubleshooter for Westinghouse Electric USA here in the Uk (supporting 101 engineers and sales across southern England) and if you think Samsung are complicated compared to Westinghouse (true Yanky fridge freezers) they are much more straightforward. Most of the problems with these types of Fr/Frzs often emanate from failed heating. Sounds strange when talking about a cooling machine but non the less true.

 

[Argus]

Sounds simple......... Automatic defrost, gets rid of the ice - electric heater in the evaporator section, initiated by either/or time/surface temperature, then terminated in the same way.
What's to go wrong?
Automatic defrosts have always been the Achilles-heel of Sub-Zero evaporation.

I worked on this stuff fitted to commercial and industrial kit in the 60s when defrosts were delivered by hot-gas or reverse-cycle.... and it was always a Friday-afternoon call out with an iceberg sitting in the midlle.

Oddly enough, big old chest freezers, Lec fridges and table-top Electroluxes carried on regardless.