USB Comunication interrupted with Arduino UNO

Hi everyone,

I'm having a problem. I've built a thermostater in order to operate an old fridge. I programmed Arduino for give me some information through Serial Communication via USB and Serial Monitor. Everything work perfect, except when the fridge's motor starts working. I think that the power variation may be confussing Arduino. I have to tell that is the board has a switching regulated power supply at 12 V 2 A.
¿How can I do? I don't want to lose connection with arduino... :frowning:

Determine whether the problem is the noise on the power line (if so, filter more aggressively), or due to EMI (put it in a metal box or move farther from the fridge), or a combination of the two. For further help, we need to know the schematic and where it's located relative to the refrigerator.