Perodua alza car radiator fan not automatically turn on but turn on with A/C only

This is one intriguing problem that still keep me searching for the solution where the radiator fan is not automatically turn on even though the temperature already exceeds its threshold which is around 93 degrees Celsius. However even at 97 degrees Celsius the fan still not automatically turning on. Only with the Air Conditioner on the radiator fan will start to spin.

The following inspections and fix were done:

• Check the fan motor - still look firm and sturdy - in fact when the A/C is on the fan running normally.
• Replaced the Engine Coolant Temperature sensor (ECT) 
• Replaced the Radiator fan relay

Despite of the above efforts the fan still not automatically turn on when the threshold temperature is met. The search continues on. What could be really the problem?

Today 28-Aug-2022 radiator fan's motor gone kaput and replaced - tested the automatic runs again but the problem continues on. The fan will turn on only if the A/C is on.

Next Checking

10A Fuse designed as E/G inside cabin compartment (Main is the relay for Radiator fans)

ST = Start relay

MG/C = Compressor magnetic clutch relay

30A Radiator fan fuse (Engine Bay)

40A Fuse AM1 (Engine Bay)