According to the knowledge base, if an abnormally high operating temperature is detected, you should:
- Make sure the rear ventilation ports are not blocked.
- Try to lower the ambient temperature.
- If the temperature is still high, go to Control Panel > Hardware & Power > Fan Speed Mode and change the fan operation to a higher speed.
The manuals also note that when the Alert LED continuously blinks orange, this can indicate system errors such as fan failure, system overheating, or volume degrade, and you should sign in to DSM for detailed information.
Sources used: [16], [2], [3], [9], [10], [11], [12], [13], [14], [15]