Monitor problem

Hello,
I am new to techspot.
So I have a pc (Msi amd a88x-G45). The problem is with my monitor.
The monitor is Asus's VX229H. The problem is that when I turn the light/fan of the room in which the pc in off/on the monitor blinks. I tested the connection with a tester but the tester light dont blinks. Even I connected the monitor with ups in backup mode so that there is no connection with the building electric connection and the monitor, but still it blinks. That means no prob with my building electricity. I tried in other 3 pin ports too in the room but same prob. I havent tried in other rooms but I will try it later. I dont know how this funny unbelievable problem is happening but it is making me crazy.

So pls help me.
 
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