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  • Registered: ‎07-10-2015
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T440 gives AC power error when batteries are present

2015-07-10, 17:41 PM

I have a T440 that just started giving errors when connected to an external AC power supply.  

When an AC power supply is connected and batteries are installed, I get an error message every few seconds that matches the one described int he KB article "ThinkPad T440p / T540p screen flicker, brightness changing or switching to airplane mode while on AC."  It looks like this:

T540p airplane mode.jpg

The screen becomes dim when this error comes up and the batteries stop charging.  The screen then becomes brighter again and the same error comes up. The cycle lasts a few seconds and repeats.

Essentially the system seems to think the AC supply is being connected and disconnected over and over.   I do not use a dock.

I have tried 3 different AC adapters (PNs 45N0358, 45N0312, and 45N0482), multiple different wall receptacles, and also tried connecting to a docking station, all with the same results.  

When no AC power is connected (running off of batteries only) everything runs normally.  

When both batteries are removed (running off of AC power only) everything runs normally.  The issue only occurs when one or both batteries are in the computer and trying to charge.

The fact that I get the same issue when connecting to a docking station rather than the normal external AC power supply, combined with the fact that it runs fine off of AC when batteries are removed, makes me think this is not a simple connection issue with the power jack or power connector.

Any input would be much appreciated!





29 Posts


United States of America

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  • Posts: 29
  • Registered: ‎01-09-2009
  • Location: United States of America
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  • Message 2 of 2

Re: T440 gives AC power error when batteries are present

2015-08-10, 7:22 AM

This is a known issue. The fix is to install the latest version of Power Manager and add the registry file described at https://forums.lenovo.com/t5/ThinkPad-W-Series-Laptops/W540-charging-bug-WiFi-OFF-no-charge/m-p/1498288#M46938 You may also want to read https://forums.lenovo.com/t5/ThinkVantage-Technologies/Power-Manager-Problem-With-quot-Enable-auto-detection-to-switch/td-p/2140997

I agree that this is not intuitive at all because the error message blames the dock rather than explaining that it is related to an Airplane Mode setting in Power Manager.

Lenovo Stuff: ThinkPad T400 (2764CTO) + Advanced Dock, ThinkPad T440p + Ultra Dock, assorted batteries, screws, and nubs
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