I have a Samsung Ecobubble washing machine that is less that 2 years old, model WF90F7E6U6W. It appears to not heat the water any more but also reports no error codes either. Given that this is a modern machine with extensive controls, how is it possible that it can be unaware that it is malfunctioning in such a fundamental way? The machine only knows when to turn off the heater when a thermometer indicates the correct temperature had been reached. Even on a 95c wash, the heater is never coming on and temperature remains stone cold. I can also confirm that the power usage never indicates any significant load from a heater element switching on. How can it not be aware of the error?
Obvious guess is that your ceramic heater element(s) are shot & I couldn't find them online in a quick search, for your model. Take it apart without effecting operation & see if you can confirm by hand or multi-meter. But, it could be a number of things from a loose connection to a dead thermistor. I'd get an Appliance Repairer if you use the heating option regularly.
The wire connecting the temperature sensor was broken. While the machine reported no errors to the user when pressing the required two buttons on the front panel (spin + option buttons?), a maintenance mode can be entered by pressing and holding the same two buttons then powering-on the machine. The maintenance mode reported the error immediately, but this mode is cryptic.
I can only assume that the error was missed in normal mode, or somehow cleared, or its a plain bug in the error reporting mode.
My wash now gets to 40c again :)