New power supplies sometimes don’t work with old MacBooks

August 11, 2010

Recently I had to buy a new power supply for my 2008 MacBook. Because having three adapters isn’t enough, when you forget to bring any of them with you on a business trip.

So I ran into the Apple store in San Francisco and grabbed a new 60 watt adapter – the one with the “L” style MagSafe connector, versus the older “T” style connectors I’ve got on my other three adapters.

Raced back to the client. Plugged it in – and it didn’t work. Spent 20 minutes cleaning my connector, trying different outlets, etc. No luck.

Headed back to the Apple store, and verified the following:

  • My new adapter works with three different MacBooks on display.
  • None of the 60 watt power adapters with “L” style connectors being used for display Macs worked with my MacBook, but all of the 60 watt adapters with older “T” style connectors did work.
  • The 85 watt power adapter at the Genius Bar did work with my MacBook.
  • The new 85 watt power adapter that Mitch @ the Bar set me up with didn’t work with my MacBook.
  • The older 60 watt power adapter Mitch extracted from the store’s repair supply stock did work.

After all of the above, I got in touch with a friend who works as a Genius at the Manhattan store. Turns out she’d just had to deal with a similar issue, and the root of the problem is that the System Management Controller (SMC) needs to be reset for some older MacBooks to work properly with new power adapters.

Apple has information about how to reset the SMC, and on that page it lists one of the reasons why you need to do this as “The battery does not appear to be charging properly”.

I’m hoping Apple updates the info found on both this page and their Troubleshooting MagSafe adapters page, to make it easier to find in the future for other users. Before Apple Stores run out of these older “T” style power adapters.

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