Your model AVR is equipped with a cooling fan that only comes on when the unit's internal temperature rises above a predetermined limit. Thanks to the massive heat sinks used in the AVR series, this temperature is rarely reached. A typical situation where the fan will come on is when the AVR is operating at a very loud volume level with program material that has sounds in all seven channels. Since this is a rare occurrence, you may never notice the fan working. In any case, when the fan does come on, the volume will be loud enough that you might not notice it. Thus, you may own an AVR for many years and never hear the fan, or see it in operation. There is no way to test the fan, and none is needed.