Samsung fridge- bad defrost sensor? Which one?

I have a Samsung RS275ACBP side by side that has problems with ice buildup on the fridge side.

Ice is building up by the circulating fan, to the point of fan blades hitting the ice, which makes a whirring noise. I think the fan is near the top of the fridge? (fan is near the bottom.)

Also, my water dispenser tank is freezing up. This is at the bottom of the fridge though, behind one of the drawers.

When I run the fridge through "forced defrost" mode a couple of times, the fan noise goes away... run it a few more times consecutively, and I can get water from the dispenser again! So it stands to reason the defrost element is working... Problem is, within a day or so the water tank freezes up and the ice builds up again near the circulating fan.

It seems a "fridge temp sensor" or "temp defrost sensor", or "thermistor" needs to be replaced; however, there are a number of different, yet similar sensors for my model refrigerator. Apparently, I have to unplug and let the fridge defrost for a couple of days before prying off the back covers, or I might damage something- so I'd like to have the correct parts before I start defrosting.

I have searched youtube, etc. but haven't found info on my exact model. It is also confusing b/c there are SO MANY problems with these so many crappy Samsung refrigerators.

Luckily, I do not have problems with the freezer, or water pooling at the bottom of the fridge. BTW, these issues only happen during the summer, I guess because it is more humid.

Any help would be appreciated! I could probably do this repair, but I'm very confused as to which part I have to replace!

Thank you for your help,
J.

UPDATE: After searching repairclinic.com, I am fairly sure I need the DA32-10105R refrigerator temp sensor. For my fridge, they have 7 different temp sensors and thermistors- so it's hard to figure out which one.

 

I'm not having much luck finding technical info on the fridge.
It sounds like to me the element is not working or the defrost thermostat is not working.

You need to access the evaporator coil and put it into manual defrost to see if the element gets hot. The problem is the defrost thermostat needs to be cold to operate.

Do you have the tech sheet for the fridge ?

 

I am able to put it in manual defrost mode, by pressing a series of buttons on the front panel, so the heating element must be getting hot... if I "defrost" it a few times consecutively, the water dispenser works again and fan noise stops because that ice has been melted away. However this only lasts a day or so before it re-freezes again.

I'm pretty sure it's a defrost thermostat, or defrost sensor? Are they the same thing? It's confusing because there are several different defrost sensors listed for this fridge. I spoke to a guy at appliancepartspros.com, who said it was part DA32-10109W, and I need 2 of them, but it seems to me that sensor is for the freezer! I will try calling a different parts place tomorrow.
I have no tech sheet....

 

Without a tech sheet or service info it's hard to answer your questions.
Most fridges have a defrost thermostat in series with the heating element that opens if the defrost temps get too high to keep the nearby plastic from melting.

It shouldn't take several defrost cycles to dethaw and it should not be frozen by the next day.

The sensor will be in the freezer and must be near to the coil. It's job is to sense low temps from ice and initiate a defrost cycle. Sometimes it gets separated and can't "read" the ice. The tech sheet usually has ways of testing the sensors.