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Samsung RFG298AARS The Big fridge DIY challenge

6 posts in this topic

Hello dear Appliantology samurais and brother grasshoppers.

This is me king_cucaracha

Get my best regards from somewhere in the latin caribbean sea. Let me explain to you my incursion on the appliantology world.


Please forgive my poor engrish since it's not my mother's language.

I always loved gadgets and cool stuff for house since I was a kid. My father (rip) was a mechanichal engineer and most of his job included Asphalt plants and industrial boilers control. Mechanics were never too appealing for me, but control is an area that really fascinates me.

He (as a good engineer) loved to go to swap meets and buy "as is" appliances, sometimes "just for the power chord" or sometimes "to open apart and find out how it works"

So in my genes there is that appliantologist vibe. Even I paid part of my college working as the Equipments Service Manager on 3 McDonald's stores on a small city in Mexico. (So I'm very comfortable talking about the infamous muitimixer that started everything, the garland and taylor grills, the frymaster deep fat fryers etc.)

Now I graduated College with a Computer Science Degree (kinda, I don't know the exact translation for my carrer in English). I work and live in an small island in south america but have never lost my appliantology roots.

Appliance History and Initial status

Suddenly when I was arriving from a long trip, a friend of mine picked me up at the airport and talked to me about a monster fridge that I may be loving (I always complained that my 7.7 ft3 fridge was not enough for my lifestyle but couldn't afford anything better) and it was at a terrific price.

I didn't even took my baggage to home and went straight to an appliance depot that mostly sells in-house refurbished appliances.

And there it was a Samsung RFG298. 29cuft of pure fridge storage in front of me. No ice makers, no door handles, inner lights didn't turn on, no water dispenser and no control board on front. but the price was terrific the equivalent to $300USD!!!!

I mean, a brand new smaller model from samsung may cost up to $3500 or $4000 usd here (remember, an island in the caribbean and with strict currency convert control)

So i got that bargains straight to home on the same day. I called a couple friends, bought some beers and made a visual inspection on the appliance. The exteriors were fairly treated, the missing handles may be fixed on the fly, and it was cooling after plugging in. So we checked the back side and big surprise.

This is what we found. (please forgive also my schematic drawing habilities I'm not an expert)


It really was "AS IS" it was just to make it cold whatever it takes. The main control PCB was ripped apart and most connection hinges were severed.

And believe me, after putting some food on it, and make it work for a couple days I realized (actually we predicted it from the first day) that i've bought a 29 ft3 freezer

So the trouble was: All motors working at the same time for 8 hours. Then was an small relief for 20 minutes. And everything started again.

Well I tought A huge freezer sounds great as i could preserve my old fridge as a fridge, but my wife said "no-no" :nono: "one or the other we can not have 2 fridges at the same time". And that's true there's not much space on kitchen for that . And since my mind and soul couldn't afford loosing that big fridgewe gave away the old fridge for an small price to a friend

Current Conditions: Trial and Error

Now with just one big freezer with the shape of a fridge the thing changed. Most of the vegetables are damaged too early, and meats, and poultry are safe for long long time (as long as you don't mind using archeologyst skills to separate one ham slice from each other when you want a sandwich)

So as it was intended from the very start we planned how to control the temperature on this big monster. I started researching and found the words "twin cooling" and i tought that it was just one of those fancy names that manufacturers use to reinvent the wheel.

So after a couple weeks we (my appliantology enthusiast friends and me) acquired a refrigeration specialized digital thermostat that claims having PID logic and several bells and whistles according to the seller. It is the autonics TC3YF http://www.autonics....03-3170D_en.pdf

The model that has capability for managing the fans was not available where I bought it so bought the one that controls compressor and defrost only

Before installing I measured the inner temps and found a fridge temp of -6ºC (~21ºF) and a freezer temp of -12ºC(~20ºF) it seemed to me very little difference between both cabinets, but a friend of mine insisted that it was just a matter of keeping the fridge above 1ºc or 2ºc ( ~35ºF) and the freezer will be almost self regulated since it is an smaller cabinet that is opened less so, looses less cold (i know, it actualy gets heat, not looses cold)

So we installed it. At first we tought that the fans should be working all time the compressor was working. But that was undercooling on the freezer. And also I misunderstood the setting up of the temp. controller and put it to defrost for 5 minutes, drip for 6 minutes every 7 hours. :wallbash:

It was real disaster!!!

I placed the PT100 sensor on several spots around the fridge cabinet until I found that was not so "nervous", because everywhere I placed the sensor tip it was a matter of 2 seconds after opening and closing the doors. The temperature raised like 4º or 5ºc what I tought was not acceptable despite the temp. controller has protection for minimum on-time and delay to startup to prevent damage to compressor the idea of having such variances on temperature made me very uncomfortable. I finally placed the sensor INSIDE the airways near the bottom of the fridge.

The fridge was pretty cold and food (specially veggies) was being maintained on optimum conditions. But fridge went really really warm. Fortunately I'm only keeping a pieces of smoked fish on the freezer (it is a good testing, since can not be damaged as it is vaccum packed and is sold to keep without refrigeration, and since is kind an oily fish I can measure how much freezing power has the freezer, if it can handle the fish fat, it can handle almost every food in the world)

We've never ever dared to open it apart from the front. Since we were never able to acquire the service manual and the exploded diagramas at samsungpartsDOTcom are almost useless for practical purpose.

But that day was 11pm. saturday and my car was at the repairshop so I tought it was a good time to be brave and become a man to be closer to the samurais.

After removing the french door, with just a crescent wrench, found it very easy to remove the freezer cover (completely tool less) and found a marvelous ice age scene on the freezer evaporator it was an almost 5" thick ice cover on the whole evaporator (nevertheless I had run 3 consecutive manual defrost cycles a couple hours before.) So I learned on the hard way, that it I needed to review de defrosting settings on the temperature controller.

So after several thinking I've found that my actual situation is like this

  • No original Compressor (It has installed a matshushita compressor that I've not been able to find info about it, but my friends say it's a 1/3 h.p. compressor)
  • No original evaporator fan motors.(I have understood after a lot of googling that the original fans work on 12V DC.)
  • Due to excess freezing on fridge. I put the compressor output at the same time to evaporator fans on the fridge and to ensure more cooling for the freezer I put the evap. fan to the freezer all time when defrost heater is not working. But that has its issues. Since I don't know if that really works to give less cooling on fridge, If it will promote more frosting on fridge evap.
  • Freezer evap. fan works all time that defrost resistant is not working. It works even on dripping time and throws water to the inner of the freezer on dripping time.
  • I don't know if the famous Step-Valve is still installed (Samsungparts exploded diagrams have not been helpfull at all since I can't find it on any section of the diagrams, only on the parts list)

Here is the schematich of my current install


In this schematich I didn't include:

An old AT Power Supply to give 12V for the Inner lights (that turned out to be leds)

A 12V car relay interacting with the magnetic switches at the top of the door that lets me control the inner lights.

The Ultimate DIY Challenge (at least for my poor skills on appliantology)

My next approach to tame this beast is more or less as follows.

Starting with these ideas

  • The main pcb will be pretty useless due to the not original motor fans, and severed cables.
  • One thermostat approach is useless since I have 2 separate evaporator and the fridge doesn't get the "remaining" cold from the freezer and gets fresh refrigerant for itself independently it is mandatory to control when and how the refrigerant goes to the fridge evaporator.
  • It is a man vs appliance fight that must be won by man. :burnin::miner:

I want to:

  • Remove the Step-valve (I will never ever loose my time controlling a step by step motor without knowing the original driver, motor type, poles orientation and several other step-motor data recquired to create a driver unless my live depends on it)
  • Replace Step Valve for a solenoid that only blocks the refrigerant to the fridge evap (I will treat the cool pantry evap and fridge evap. as the same unit for this application)
  • Create my custom temp controll using a Siemens Logo! PLC (since I don't know if currently are "generic" temperature controllers that can manage 2 sensors.)

This PLC has the capability of manage via an analog extension specialized on PT100 sensors, 2x PT100 sensors at the same time.

Has 8 digital inputs and 4 digital outputs (By digital I mean, ON/OFF states, no actual digital technology recquired for inputs)

In case of recquiring more digital outputs I can get another expansion module

Migrate Control schema to 12/24v (that means changing relays, so I can manage 12/24v inputs recquired by PLC)

I've already designed the sketch of the program for the PLC and has the following premises

  • 2 PT-100 Temperature Sensors as analog inputs One placed on the freezer and other on the fridge.
  • Freezer temp. Sensor will control The compressor operation
  • Fridge temp. sensor will control the solenoid operation.
  • Both of them will be supedited to the Defrosting Timer that will preserve my current settings that have proven to not allow excesive frost and made a real quiet refrigerator. (·4 Hrs cycle, 17minutes defrosting, 6 minutes dripping)
  • Neither Compressor nor evap fans will work during defrosting and dripping time
  • Doors open will stop fridge fans.

Questions and yelling for help

  • Have anyone seen the service manual for this appliance?
  • Does somebody knows where to find this "step-valve" to verify if it is still installed?
  • What for is the press switch on top of the fridge cabinet (next to the left magnetic switch)?
  • Is there a way to open apart the Left door to change or install new wiring instead of the water tube?
  • Do you know where to get more information about this appliance to make a better project?
  • I made work the the freezer lamp switch and operates when is actuated by hand. But it doesn't actuate with the door. Maybe some part missing on the slider assy of the french door?

I've read that the Twin Cooling system injects "the exact amount of air" to the fridge to keep high humidity rates. I believe it is made by varying the voltage on DC Fans. Since my fans are 110v AC. And I'm not willing nor able to spend on a frequency changer and not wishing to make one interacting with the plc analog inputs. Do youy think it will be a good idea to set timers in the PLC program to turn on and off the fans periodically or under more complex rules when is near the set point?

Do you have any objections? Complains or suggestions about this project?

Will this project take me apart from the appliantogy zen?

Do you have ideas to add for this project?

Will be more than welcome since refirgeration has never been on my strong side.

Wishing you best regards

Tropical Greetings from your friend


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Need appliance parts? Call 877-803-7957 now!

I didn;t have time to read (nor follow) your entire ppost,

but, why didn't you just fix the original problem ?

It may have been just a bad Thermistor sensor...

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I didn;t have time to read (nor follow) your entire ppost,

Sorry if the post is too long to read and follow. I Present my apologies, but since it's my first post I tought that some netiquette as introducing myself would be nice

And this is a DIY project, more than a repair, I tought that It should be better that people in the forum get the most information about it. For a better knowledge of this idea and if someone has ever faced this kind of situation. If it is feasable or if I'm completely nuts.

If you think that it is better in another section or not appropiate for this forums I would gladly move it to another section or forum. This was the only section I saw this could fit (I use to read the rules of every forum I join.)

but, why didn't you just fix the original problem ?

It may have been just a bad Thermistor sensor...

No bad thermistor (Not even a good one :lol: )

Bought the fridge without a thermostat, just an 8:20hours defrosting timer and all fans and compressor tied together running for 8 straight hours and relieving for 20 minutes for defrosting.


Thanks for your reply.

Greetings from the caribean :beach:

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This project is more an end-of-the-world scenario---like the Mad Max movie.

Most (if not all) appliance servicers are not engineers and therefore by training we are taught to adhere to accepted safety standards. That usually means NOT altering the intended design function of an appliance.

Your project is interesting though---because it is so out-of-the-ordinary.

It's not impossible to rig the refrigerator to "function" without the digital controls---it is just something that most of us don't encounter very often.

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Hello dear Appliantologists. I hope you had a nice NFL season start. (mine was great! My team won LOL )

Thanks for taking the time to read this thread and to give your opinions. Actually I didn't think that it will be replied so fast!!!.

Thanks for everything

This project is more an end-of-the-world scenario---like the Mad Max movie.

Definitely you're right and you've talked to my wife. She inmediately adviced when we brought the fridge to home that "The fridge will end up like

Back to the Future's D'Lorean"

Most (if not all) appliance servicers are not engineers and therefore by training we are taught to adhere to accepted safety standards. That usually means NOT altering the intended design function of an appliance.

I also received that training and I'm very used to the stay-on-what-the-book-says approach, that's why I'm so nervous about this project.

It's not impossible to rig the refrigerator to "function" without the digital controls---it is just something that most of us don't encounter very often.

I really hope so, Thanks for your reply and I will surely receive very well al of your suggestions.

.. a standard mechanical Thermostat would have worked...

Actually it didn't I:(

I forgot to put on the first post that it was the first approach, but it didn't control temperature very well (I'm thinking that the salesmans didn't understand and sold me a thermostat for frosting fridge") It was more like an on/off manual switch for the compressor

The problemis that since the Samsung's "twin cooling" system actually has 2 evaporators for just one compressor. The main difference between both cabinets is very small

fridge temp of -6ºC (~21ºF)

freezer temp of -12ºC(~20ºF)

It normally controls the ammount of refrigerating gas going to each evaporator using a 3-way valve.

That's why a normal 1-thermostat approach doesn't apply on this.

I'll make further research and keep you informed (if you're interested of course)

All your suggestions are welcome

I'll be writing you on the week

Thanks and best regards to all

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