Wednesday, October 19, 2011

A dead MacBook Air power adapter is magically restored. SMC problem?

The power adapter for my 6 week old 11" MacBook Air failed overnight (45W MagSafe power adapter with "L" style connector $80!). No glowing LED, no charging. Happily a friend's works, so I know the Air is ok.

Still, it's most annoying -- especially since today's lunch trip to a nearby Apple store ran into their Jobs memorial closure.

Naturally I'm inclined to believe this is a national disaster, but this isn't a trending topic anywhere. So it's probably just bad luck.

Researching this did lead me to a related topic of interest. It's safe to use a higher wattage adapter with the Air, specifically the current MacBook and MacBook Pro adapters ...
Intel-Based Apple Portables: Identifying the right power adapter and power cord--US
... Power adapters for Intel-based Apple portables are available in 45W, 60W, and 85W varieties. Although you should always use the proper wattage adapter for your Apple portable, you can use an adapter of a higher wattage without issue.
For instance If you have a MacBook (13-inch Late 2009) that normally uses a 60W adapter, you can also use an 85W adapter with that computer. You would not use a 45W adapter with that computer; it would not provide enough power for that MacBook...
I've read elsewhere that using a lower power adapter might allow the machine to function, but not to charge.

The article, incidentally, tells us the removable AC plug on Apple's power supplies is a "Duckhead". Who knew?

Update: On the advice of Dan Swift (see comments), I tried a fix that I thought was 90% crazy. First I confirmed I didn't have a 'stuck pin' problem. I checked all connector pins were moving and out. Then I charged it for 30-45 minutes on a friend's 'good' charger. Then I tried my charger. Now it works again.

This is the weirdest thing I have seen in years. I assume there's no OS in the (bloody $80) charger, so I assume this is a MacBook PMU glitch that will need a firmware update to fix.

Thanks Dan. I've changed my post title to make this easier to find.

I've posted on this to Apple Discussions.

Update: It's back to not working, which feels saner to me. I did reset the SMC, which may help when "The MagSafe power adaptor LED doesn't appear to indicate the correct activity". So it's to the Apple Store sometime soon.

I did find an article on a similar problem from 2008 that tells me that firmware issues can alter charging behavior: "In certain situations when you connect a new 60W or 85W MagSafe power adapter to the MagSafe port of an older MacBook or MacBook Pro computer, the adapter may not charge the computer and the LED indicator light on the MagSafe connector of the adapter may not illuminate."


Dan Swift said...

We've seen this before -- sometimes plugging in a 'known good' power adapter, letting the laptop charge for a few minutes, then plugging in the old one brings the charger back to life. I don't know why it would do that ... but sometimes it does.

JGF said...


It worked.

I would have bet that what you were seeing was a problem with the retractable pins popping out on their own, and the 'good charger' behavior was coincidence.

So I was very careful about the pin position. Then I charged for about 30-50 minutes, but not fully.

Now my charger is working.

I assume it's a MacBook PMU glitch. This is the weirdest thing I have seen in years.

Dan Swift said...

Glad it helped!!!

JGF said...

Dan, I've been looking all over for stories like this. I can't find any.

I also don't understand how this can actually work. I assume that the adapter would have to have a unique identifier or some state behavior. It's just deeply weird.

You said "We've seen this before". Where did you see it? Have you written about it elsewhere?

Like I said, this is the strangest thing I've seen on my Mac.

Armen said...

I'm glad I found this article.

Plugged my the adapter for my 2011 MBA in today to find that it wouldn't work.

I don't know how I came across this site, but after reading your solution, I stuck in my old shape MBP adaptor in for a few seconds, then went back to the new one. Nothing. Still dead.

Thinking it was just dead, I went back to the old adaptor and started browsing. After 30 minutes or so, I thought I'd try again.

It worked!!

This is as odd as two left feet! I simply can't understand the reasons for this, and now I don't know what to do. I'm going past the city tomorrow and I'm wonder if I should visit the Apple store, or just leave it until I know it's dead.

If you can add anything to this that you've discovered since the last update, it would be much appreciated. Otherwise, thanks for giving a temporary fix of sorts.

amcg said...

I've had this problem with the new MBA.

Charger randomly stopped working.

Originally thought duck-head was broken. Used extension cable. Charger working again. Charger then broke again. Got replacement duck-head. Working again. Then it stopped working again.

Brought everything to the local apple store where the guy plugged everything in then "forced" some sort of update on the Mac. Working again.

That was two days ago.

And the charger has now stopped working again.


Anonymous said...

If I heat mine with a hair dryer or bake it near my woodstove for a few minutes it is fixed... there is a design flaw unrelated to the cord.

Eric said...

I have two 45w chargers for my MBA. They are not always working. The Apple store wants me to by another one since my old ones are not covered anymore. Just found out the new MBA is using a new type of charger. Apple might fixed the old problem but never admit there was a problem on the old design.