Auto sleep mode not Working in Macbook Pro Unibody

[Aandaleeb151]

I have a MacBookPro Unibody which runs on Mac OS X Snow Leopard. The Macbook is working fine but with it has some minor problems. The Auto Sleep mode in Macbook is not working. Whenever I put the Macbook in sleep mode, the system shows that it is preparing to sleep but it does not. It only goes to sleep mode if the LID is closed otherwise it does not go to sleep mode. So if any of you are facing the same problem as I am facing then please suggest me some solutions. Can this be because of some hardware problem? or is it a software issue?

[Barclay]

Looking at the Problem it is looking like a operating system issue. Some files of the operating system are corrupted i suppose and needs to be replaced. In sleep mode the system is in stand by mode and certain files are needed to be executed so that the system can be revived from the sleep mode. If this files are not executed, the operating system does not let the system go in sleep mode. Hence Replacing the files will solve the problem. If you have the install disk for snow leopard then you will be able to repair the Operating system without any problem. You can also choose the Install/Archive mode to install a fresh copy of operating system without removing the installed applications.

[Theodot]

Check the Power saving options of the Macbook first. Modern day Macbook come with lot of power saving features which sometime prevent the Macbook from going to sleep mode. To check the Power saving features, Go to System preferences and select Power management option. In that category, see if the Prevent System to go in Sleep mode is enabled or not. If it is enabled then disabling it will solve your problem. If it is disabled and still the system is not going in to sleep mode then there is some other reason for the Macbook not going into sleep mode.

[Tomaz]

There must be some applications which are running in background which are preventing the Macbook to go in to sleep mode. As the Macbook goes into sleep mode if the LID is closed and not by using software method, this is a issue related to software. Open the activity manager and disable all the running processes except the system process and see if the Macbook goes to sleep mode. If the Macbook goes to sleep by terminating all the processes then find out the application which is creating problems while putting the Macbook in sleep mode and uninstall it.

[Simond]

You can try doing a PSU and PRAM reset can see if it works. Many problems which are faced in Mac Systems are solved by doing PSU or PRAM reset. To do a PRAM reset follow these steps:
1) Shut down the system
2) Press Command, Option, P and R key together While starting the computer.
3) Keep these keys pressed till three start up beeps are heard.
4) Release this keys as soon as the 3rd Beep is heard and let the system boot.
To Perform the PSU reset follow these steps :-
1) Shut down the Macbook.
2) Disconnect the AC power source.
3) Remove the Battery and locate the PSU reset button.
4) Press the PSU reset button and let the system sit for 1 min
5) After 1 min connect the battery and boot the system
Hopefully doing a PRAM and PSU reset will solve the Problem.

[Gonzo]

There must be some scheduled tasks on your Macbook which are preventing it from going in sleep mode. Check if there are any scheduled tasks on your Macbook. Many applications schedule their updates when the system is idle, hence when you are putting the Macbook in Sleep mode it is possible that update process of such an application is running which is keeping the Macbook pro from going to sleep. Disable all the automatic updates of all the applications installed and also disable all the scheduled tasks. Then check if the Macbook can go to sleep or not.