When I woke up last night it was a little windy outside, so I decided to unplug my MacBook Pro because the power tends to flicker here in Alaska. When I picked up the MacBook I noticed that it was very warm, even though the lid was closed and it was in Sleep Mode. This morning I decided to dig into the “Why is my MacBook hot even though the lid is closed and it’s in sleep mode” question.
“Warm MacBook” troubleshooting
After a lot of googling I found that people have a lot of theories about why a MacBook is warm in sleep mode, but the most logical way to troubleshoot the problem goes as follows.
First, run this command from your MacBook/MacOS Terminal application:
log show | grep 'Wake reason'
That log command can take a long time to return, so if you’re only interested in the most recent events, be sure to search for the current month as well. I’m writing this in March, 2018, so that change looks like this:
log show | grep 'Wake reason' | grep '2018-03'
When you do that you’ll eventually see output that looks like this:
2018-03-21 12:33:39.134535-0600 0x73 Default 0x0 0 kernel: (AppleACPIPlatform) Wake reason: XHC1
2018-03-21 12:33:39.134539-0600 0x73 Default 0x0 0 kernel: (AppleACPIPlatform) Wake reason: XHC1
2018-03-21 13:13:41.189154-0600 0x32af8ab Default 0x0 0 kernel: (AppleTopCaseHIDEventDriver) [HID] [ATC] AppleDeviceManagementHIDEventService::processWakeReason Wake reason: Host (0x01)
2018-03-21 14:01:36.686218-0600 0x73 Default 0x0 0 kernel: (AppleACPIPlatform) Wake reason: XHC1
2018-03-21 14:01:36.686220-0600 0x73 Default 0x0 0 kernel: (AppleACPIPlatform) Wake reason: XHC1
2018-03-21 14:23:03.385855-0600 0x32e0a7c Default 0x0 0 kernel: (AppleTopCaseHIDEventDriver) [HID] [ATC] AppleDeviceManagementHIDEventService::processWakeReason Wake reason: Host (0x01)
2018-03-21 15:37:57.871937-0600 0x73 Default 0x0 0 kernel: (AppleACPIPlatform) Wake reason: XHC1
2018-03-21 15:37:57.871940-0600 0x73 Default 0x0 0 kernel: (AppleACPIPlatform) Wake reason: XHC1
2018-03-21 16:19:23.315217-0600 0x3332cbe Default 0x0 0 kernel: (AppleTopCaseHIDEventDriver) [HID] [ATC] AppleDeviceManagementHIDEventService::processWakeReason Wake reason: Host (0x01)
2018-03-21 17:24:52.436300-0600 0x73 Default 0x0 0 kernel: (AppleACPIPlatform) Wake reason: RTC (Alarm)
The important thing you’re looking for in that output is what comes after “Wake reason.” In my case I saw this over and over again:
Wake reason: XHC1
A little more googling initially showed that “XHC1” refers to Bluetooth devices, but a little more googling on top of that showed that it may refer to both Bluetooth and USB devices.
My solution
In my case, the solution was easy: My Apple MagicMouse battery died yesterday, so I connected an old Dell USB mouse to my MacBook yesterday afternoon. As a test this morning I disconnected the USB mouse and let the system sit for a while. When I came back, the MacBook was cool to the touch, so it seems like the USB mouse may have been what was causing the MacBook to wake up and keep running even though the lid was closed.
Note: “Wake reason: RTC (Alarm)”
As you can see in the output from my log command, you may also see entries like this:
Wake reason: RTC (Alarm)
At the moment I don’t know exactly what “Wake reason: RTC (Alarm)” means. I do know that RTC stands for “real time clock,” and my assumption is that these entries refer to background processes that are started by the MacOS version of crontab, but I can’t confirm this yet.
Possible problem: Energy Saver settings
There are a couple of other possible system preference settings that can also cause your MacBook to wake up even if the lid is closed. One of the settings can be found under the “Energy Saver” area of your system preferences:
If you have any of these settings enabled, your MacBook may wake up even though the lid is closed and its in sleep mode:
- Prevent computer from sleeping automatically when the display is off
- Wake for Wi-Fi network access
- Enable Power Nap while plugged into a power adapter (also shown as, “Enable Power Nap while on battery power” under the Battery tab)
If any of those settings under the Power Adapter or Battery tabs are checked, try un-checking them and then run a test to see if your MacBook is still warm when the lid is closed.
Possible problem: Bluetooth settings
Another possible problem involves your Bluetooth settings. If you go to System Preferences, then click Bluetooth, then click the Advanced button, you’ll see the following dialog:
On this dialog the “Allow Bluetooth devices to wake this computer” is a possible problem, but — and this is a big but — if you do what I do and use your MacBook with an external monitor, with the lid closed, and a Bluetooth mouse and keyboard, you’ll probably want to keep this enabled.
That being said, if you always use your MacBook as a laptop and only want the MacBook to wake up when you open the lid, you can un-check this setting.
More information
I’ll keep digging into this problem, but for now I’ll just share a few links where you can find more information.
First, this Apple support page has these notes: Your Mac might wake for these activities:
- Network activity that uses the Wake on Demand feature. Examples of network activity include iTunes sharing, photo sharing, printer sharing, file sharing, and using Back to My Mac.
- Enhanced notifications from FaceTime, Messages, and other apps and services.
- Bluetooth activity. To prevent Bluetooth devices from waking your Mac, choose Apple menu > System Preferences, then click Bluetooth. Click the Advanced Button, then deselect “Allow Bluetooth devices to wake this computer.”
Next, this Apple support page has sections on “If your Mac doesn't go to sleep when you expect” and “If your Mac wakes unexpectedly.” Please see those pages for more details.
Summary
I hope this look into “Why my MacBook was warm when the lid was closed and it was in sleep mode” is helpful. If you have a similar problem and the solution I shared here doesn’t help, feel free to leave a comment below and I’ll see if I can help.
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