If you feel hot air being blown from the back then you know it's cooling properly.
It's not the perfect way to tell but it's at least a way to tell that the heatsinks are hot (which should be the case as they take the heat from the CPU/GPU ;p)
It's not the perfect way to tell but it's at least a way to tell that the heatsinks are hot (which should be the case as they take the heat from the CPU/GPU ;p)