Samsung refrigerator model RF26J7500SR/AA - Fresh Food upper fridge area evaporator defrost heater testing

[kryto8823]

I removed the evaporator defrost heater from the fridge area (upper section of french door fridge) for testing. This one has the defrost thermostat in series with the heater. (DA47-00244U)

I'm am trying to understand the resistance readings. I'm getting 141 ohms at room temperature. And I did put 120 volts to it at room temperature, it does heat up hot for most of the heater rod except the ends stay cool, maybe 3" long each end is cool to touch.

The defrost thermostat has 60/40  101514 printed on it. So I think that means at 60 F, it opens (no continuity thru it) and at either 40 F or 20 F it closes to heat up to defrost evaporator.

so at room temp (72 F) it should be open, meaning no continuity from wire connector to wire connector. The 141 ohms means some continuity, and the fact that it heats up means the in-series defrost thermostat is "closed" ?? 

please help me understand my readings before I spend $$ on new defrost heater.

 

Thank You

 

[Vance R]

For the bi-metal usually 60-40 means it open at 60 deg f and will close at 60 minus 40 which is 20 deg.  This is all assuming it is Fahrenheit, in Celsius 60 deg is 140 deg f which is what most samsungs use a safety fuse. The defrost cycle is controlled by the thermistor and the bi-metal is use as a safety. Need to check the defrost thermistor for proper resistance when disconnected or voltage while operating.

[kryto8823]

thanks Vance R, the thing that I'm trying to understand, is if the bi-metal which is in series with the heater is to OPEN at 60F and I'm testing both bi-metal and heater at same time at 72 F, it should be an open circuit, but I'm getting 141 ohms, and then when I put 120 volts to the thing, the heater comes on, it gets hot. (this is testing with bi-metal / heater out of the fridge.)

If that bi-metal is OPEN, the heater should not even come on. Am I missing something.?

Also, the sensor DA32-10104N attached to the evaporator tube.
5410 ohms @ 73 F and 12450 ohms @ 34 F which I believe is ok. I am going to replace sensor anyways.

 

[Vance R]

Think the bi-metal is using Celsius "60" which is 140 deg fahrenheit so it would be closed at 72 deg f.  

[kryto8823]

thanks, I believe you are correct, it must be in celcius. I ordered another defrost heater and it showed the same results. 140 ohms resistance, and when 120v applied to it, it heats up at 70 degrees room temperature. Only difference is the new heater works better. It heats up along the whole rod. The old heater had cold spots at both ends. Fridge is running now, temps so far, are good. Thanks for your help.