Samsung SR-S2028 fault diagnosis

Firstly I would like to say I have read with interest a lot of the previous posts from people with the same fault as I have. I know I am repeating the same question but I would prefer to do that and be sure before I spend any money on parts I may not need!

To the problem:

I have a 6 year old Samsung SR-S2028, BOM Name SS20WH3/XEU. I noticed a few days ago that a puddle of water had appeared in front of the unit. Didn’t think much of it at the time thought it was the dogs being messy with their drinking water! However I then noticed that the milk in the fridge was not as cold as usual, checked the freezer and found the ice was melting. After reading previous posts I made some observations and checks:

There is condensation on underside of shelves.
There is no ice build up around the evaporator or fan.
The fan is working and there is good airflow.
When the top two buttons are pressed for 10 seconds the panel flashes, goes blank and then returns to normal. As a test I unplugged the fridge fan connector then tried again, the bottom segment lit so faults are being registered.
The unit appears to enter defrost mode but does not exit except when the unit is switched off and on again.
I noticed that the drain heater is hot but the main heater is not.
I have metered the heaters and defrost sensor using the information on this sites problem guide for samsung rs21 modules, http://www.ukwhitegoods.co.uk/help/fix- … ezers.html The main heater is open circuit, the drain reads 2.14ohm and the defrost sensor is 15ohm at approx 0’C althought this constantly dropped as it warmed up. The thermal cutout has continuity. Although this is not the exact model I think the readings are probably not far off, it certainly means the main heater is dead.

Based on other posts I believe I need to change the main heater (and sensors as they come with it). What I don’t understand is why. Surely if the main heater is not working then defrosting wouldn’t be able to take place so ice should build up. I guess that the drain heater would defrost some if not all depending on how much has built up. Why, however, doesn’t the defrost sensor pick up that the temperature has risen and start the cooling cycle? Can the sensor be faulty too, the reading was higher than listed on the newer model? Or is there another fault altogether?

If anyone can also tell me where I can purchase the correct evaporator unit it would be appreciated.

Many thanks,

Brian