My frost-free 2 door (top-freezer) 280 Litres refrigerator is only 4 months old and stopped working altogether on Christmas eve. When called for service under the warranty, the defrost timer was reported faulty and replaced. But my fridge kept running non-stop all the time. When I again called the service personnel, they reported that it is "normal behaviour" as long as there was proper cooling (which is the case). But got concered as my energy meter was galloping and as my fridge was not behaving like this before. The thermostat (inside the freezer compartment) is set to 3 on a scale of 9 and the rotaty switch in the lower compartment (I think it regulates the air supply) is set to "Normal". When I rotate the thermostat to lower setting (2 on a scale of 9) after it has been running for a while, I can hear the compressor stop. But again it keeps on running without any halt. Could this be a faulty thermostat? To my surprise, even though it is running all the time, there is no "over cooling" of foods (the cooling effect seems to be the same as before).

The fridge never kicked into the defrost cycle at all. When I manually turned the defrost timer to the defrost cycle, it would never kick back to the run cycle. So I doubted if the defrost timer is getting power to run its motor at all.

I called the service personnel again and they have once again replaced the defrost timer (when I wasnt at home). And the same behaviour continued. So, I sat down to understand the circuit diagram on the back plate and found that power was routed thru the "defrost heater" and then a "thermal fuse" to the defrost timer motor. With a line tester, I figured that the defrost timer motor did not get any power at all (no matter which cycle I manually kicked it in). Could this be because of blown thermal fuse? I also noticed a "bi-metal" switch in the circuit diagram (defrost thermostat I think). Could this be because of a faulty bi-metal switch. Or is it a combination. i.e a faulty bi-metal switch has allowed the defrost heater to over heat and blown off the fuse?

I dont want to open up the fridge as it is still under warranty. But atleast I want to ensure that the service personnel I have to call again are doing the right thing to fix the problem. I dont want to have the "defrost timer" changed for the third time without any reason.

Any thoughts on this are welcome.