Replacing NTC Thermistor with an SMD Resistor ..#2

Thread Starter

A1gg

Joined Apr 5, 2021
3
You have bypassed a safety mechanism. Anything bad that happens is now on your shoulders, not mine. Particularly, if there is the potential for fire, I would not do what you have done nor condone it.
Speaking of NTC sensors. My old ( like ~20 years old) Washing machine's NTC thermistor is suspiciously faulty. I want to replace it with a variable pot resistor. I read 5 Volts DC on the open circuited NTC terminals of the Motherboard of the washing machine. This voltage goes down to 4.3 V when a 10k Ohm resistor is connected instead of NTC.

If I open circuit a NTC sensor will the machine heat the water unboundedly or not heat it at all? There should be a way to trick the machine into thinking it needs to heat the water. At least for a while, right?

Mod: link to old thread.E

https://forum.allaboutcircuits.com/...stor-with-an-smd-resistor.175087/post-1661626
 
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LowQCab

Joined Nov 6, 2012
1,189
How have You determined that the NTC Resistor is faulty ?
They virtually never "just fail" for no apparent reason.
They are generally not a part that experiences any significant stress.

Fooling the Controller is a BAD idea.
Obtain the exact replacement part,
or at least one that is estimated to have very similar characteristics.
.
.
.
 

Thread Starter

A1gg

Joined Apr 5, 2021
3
How have You determined that the NTC Resistor is faulty ?
They virtually never "just fail" for no apparent reason.
They are generally not a part that experiences any significant stress.

Fooling the Controller is a BAD idea.
Obtain the exact replacement part,
or at least one that is estimated to have very similar characteristics.
.
.
.
I thought it was faulty because it has a resistance of 4.8kOhms at 14 degree Celcius. The variation in this value seemed a little bit "off" because I noted no decrease (Negative-Temperature-Coefficient) in resistance when I put hot water into the washing machine chamber ).


Correct me if I'm wrong, but doesn't the NTC component gets some kind of under stress by heating up and cooling down cycles of the washing machine? The constant expansion and contraction of the material inside maybe caused it to "crack". Is this a negligible possibility?

It does not carry much current and it is not under a kind of dissipative stress, you are certainly correct about that.
 

BobTPH

Joined Jun 5, 2013
3,823
What is the point of having a temperature sensor that cannot survive temperature changes? I don't think the temperature change between hot and cold water in a washing machine would put much stress on anything.

Edit: The thermistor on my 3D printer goes between room temp and 300C without breaking.

Bob
 

ElectricSpidey

Joined Dec 2, 2017
1,907
I thought it was faulty because it has a resistance of 4.8kOhms at 14 degree Celcius. The variation in this value seemed a little bit "off" because I noted no decrease (Negative-Temperature-Coefficient) in resistance when I put hot water into the washing machine chamber ).
Measured in or out of the circuit?
 
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