No Audio OutPut When Cooling Fan Starts

i recently bought a sansui rz 6880 av 5.1 ch receiver.The problem is when i connect the output speakers and switch it on, it only plays for several seconds.When the cooling fan automatically switches on, the audio output goes silent. When i toggle between tuner,dvd,cd,aux,vcr or tape the same thing happens. i have tried using 5 x 8 ohms speakers but the problem persists