Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
Your Mac Does Not Sleep?
The Mac system consists of a feature of sleep mode which has dual benefits. Firstly, it saves the power on the system and secondly it enables the user to quickly and easily resume the work which has made it a most used Mac feature. For configuring the settings as to when the system should go to sleep can be done from the energy saver system preferences. Moreover, the power button can also be used in order to invoke the sleeping habits of the Mac.
Common features of the sleep mode can be accessed through System preferences as to when the system should go to sleep and whether the modem and LAN access should also be taken away with it. In addition to these features, the user can also make use of the Terminal command “pmset” for the purpose of adjusting some features such as making the system to awake when the power source to it is being changed, variations in the brightness of the display when the laptop is being used on battery power plus the changing in the default sleep mode.
Although, the sleep mode is good for the system’s health, but there are various instances when the system can face serious issues during its sleep mode. The occurring of problems is backed by several reasons such as issues in the software configuration, malfunctioning in the peripheral device and settings of power management.
There are basically three types of sleep modes in energy saver preferences and are explained as follows:
Hard disk sleep: if the hard drive is set idle for a longer period of time, it will automatically stop rotating in order to conserve energy. Apart from a minimal reduction in the operating sound of the system, the user can definitely figure out that the system is sleeping. It will only wake up only when a new application requires be reading from or writing into the disk and a slight delay in this action is noticeable.
System sleep: usually referred to as the sleep mode, the system as well as the hard drive on it will stay in a state of low-power. The power indicator beneath the display screen will either flash, pulsate or will turn its color into amber, depending on the Mac system you have. In order to release it from the mode, press any key on the keyboard or click on the mouse.
Display sleep: in case a display sleep occurs, the screen will either go black or will be occupied with the screen saver you configured but, the applications will remain active. The power indicator will change eventually so that as to indicate that the system is running on a low-power mode. Waking it up requires the same process to that of the system sleep.
If there is a situation in which the Mac operating system is unable to go to sleep, the first step here should be to reset the system hardware settings. These settings include the resetting of System Management controller (SMC) plus the Parameter RAM (PRAM). After the settings have been made, the Mac system will require a restart after which the sleep settings must be configured again.
Apart from making changes in the hardware, problematic issues that are confronted with the software configurations may be another reason as to why you’re Mac does not go to sleep. Resolving this matter might require the deactivation of some third party installers that are present on the system especially those who are operating in the menu bar or in the background. Start the system on Safe Mode in order to determine whether the sleep mode is working properly within a minimal boot environment. If the result comes out to be positive, carry on the program settings by disabling them in a systematic manner.
This action might turn out to be useful for those applications which have the tendency to install kernel extensions as it might change the way through which the kernel comes in contact with the hardware. On the sad side, Mac operating systems does not have any troubleshooting utility through which the kernel extensions can be handled. Apart from the Safe Mode method, the user can also create a new account and then log into it so as to see whether the safe mode is working in this section or not. If the result is positive, then it is sure that the problem area is the main account which is intersecting the system’s sleep function.