Our refrigerator commonly would decide to become a freezer. Call it a stipix or write it off as just being overly enthusiastic, either way it would commonly freeze our water filter and crack the housing or worse, upset the wife because the vegetables she was planning on using for dinner are now frozen solid. Rather than being variable, the temperature control switch seemed to have two positions, off (sauna) or constantly on (freezer mode).
This particular fridge is a Frigidaire model no. FRS26KR4CQ0, however if you have found this post you likely have this same issue with another model as it is a common issue for many side-by-side fridges made by the Electrolux Home Products company.
After cracking the third water filter housing I couldn't take it anymore. Okay so the wife may have finally pushed me to find a solution. I started my investigation and soon found that the temperature control switch wasn't performing as expected. It has a massive deadband where it will close but won't open until it is orders of magnitude colder. Okay, slight exaggeration, but it was clear that everything else was working.
The way the temperature is set is actually pretty simple. There is a basic thermostatic switch which sets the temperature of the freezer portion. The temperature control for the fridge side is a single pole-double throw (SPDT) switch which sends power to a set of limit switches which control power going to a motor which opens and closes a door to the freezer. I was able to figure that all out because Frigidaire was kind enough to provide a wiring diagram on their website.
http://manuals.frigidaire.com/prodinfo_pdf/Anderson/240389610.pdf
I have highlighted a portion of their diagram which shows the operation of the circuit.
The fridge thermostatic switch is circled in red. The one next to it is for the compressor/freezer function.
Power comes in on the common terminal on a black wire. It is highlighted in yellow in this image. Depending on if the switch is off or on, power comes out on the normally open (NO) purple wire, or the normally closed (NC) pink wire. Once power comes out on either wire it goes to the two limit switches which pass power to the damper motor and it either opens or closes the damper until it reaches a limit switch cutting power. When the thermostatic switch changes the process repeats but moves the motor and damper back the other direction.
So that is a pretty cool circuit but if the thermostatic switch is junky the door won't open and close as needed to maintain a desired temperature range.
The standard fix for this involves replacing the entire temperature control assembly; thermostatic switches, logic board, and damper door assembly. I am not sure why but every help topic I found during my online research, all the experts agreed that the entire assembly should be replaced with the updated unit which cures this issue. I can say for sure that the switch is updated but they must have updated more of the assembly because you can buy just the updated switch but several people said they still had issues with food freezing. Weird.
I could have picked one up from Appliance Parts Pros but I couldn't swallow the price for the specific revised unit for my model fridge.
http://www.appliancepartspros.com/frigidaire-control-box-kit-5304482075-ap5176342.html
I wasn't going to buy that part but I would like to recommend that site for other issues you may encounter on basically any major appliance. They are a great resource and most of their prices are competitive.
I immediately started coming up with another way to fix this. Jumping to a digital temperature controller wasn't really much of a leap. I selected a TS2-010 from Dwyer Instruments because it is a well known commercial controller which could withstand the environment of a refrigerator and had a relay output with both a NO and NC set of terminals making it a nearly direct swap for the mechanical thermostatic switch.
Click on the image below to purchase from Amazon.
I paired it with a TS-5 probe
Once it all arrived it was time to get to work.
1. Clear out the top area of the fridge and unplug it. Do this quickly as your fridge is going to remain off until you complete this modification.
2. Remove all the 1/4" hex screws to take off the plastic shrouds that house the temperature switches, control board and damper door.
3. Unplug the wiring harness and gently remove the shroud assembly being careful to slowly pull the temperature probe from the freezer side and set it on a clean surface to being hacking.
4. Remove the temperature switch for the refrigerator side and remove the wires.
5. Mark and cut an opening for the new controller. I found the area where the logo is to be the only area big enough in the shroud that could hold the new digital controller.
6. Wire it up. This part is actually pretty easy but you will have to extend the wires to reach the new location. I recommend solder and heat shrink.
The common wire (black) has to go through the relay on the common terminal labeled 10 but it also has to power the controller so it needs a jumper to go to terminal 8. Terminal 7 needs a neutral wire for the other side of the power input. I tapped the neutral wire which supplies the light bulb since the switched wire is the hot wire and the neutral is always available. I had to test that to make sure the controller would remain powered after the door was shut. The pink wire goes to the NC terminal and the purple with white stripe wire goes to the NO terminal. Then connect your temperature probe to terminals 1 and 2. Neatly organize your wiring to prepare for reinstallation.
7. I left the temperature probe wires long so I could move it around if needed but I found if I left it hanging down at the back of the fridge it worked well.
8. Reinstall the hacked assembly, power up the fridge and program the setpoint on the controller. I set mine to 34 degrees F with a 2 degree differential so it would begin cooling the fridge when it goes up to 36 degrees. I also disabled defrost (the controller board already takes care of that). You may also want to set a minimum stop time to prevent a short cycling scenario where it closes the damper and then has to immediately reopen it because you opened the door to the fridge.
9. Optional: You may want to add some object to the temperature probe tip to improve stability.
I used a small piece of aluminum for this task. Its silly looking but the whole project is kind of silly and it does work.
The old temperature control switch is still there but only so it doesn't leave a big round hole where it once was. It's not hooked up to anything. Also note the new water filter housing (4th one for this fridge).
10. Profit! Sit back and enjoy the praise from your spouse or significant other... well its nice to think that could happen, right?