Peculiar problem regarding bottom case and 13" MacBook Pro

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Peculiar problem regarding bottom case and 13" MacBook Pro

hey fellas, this is sort of an in-depth question for the seasoned apple hardware technicians out there. I am working on a mid-2009 13" macbook pro that, with it's bottom case on, runs the fan at full speed even though it is not hot (blowing cold air out the back). In addition, the airport shuts off (but is still seen in system profiler).

With the bottom case off, the computer works perfectly. I have replaced the logic board twice and a replacement bottom case has also not resolved the issue. I had tried the bottom case from another 13" MBP and at the time the symptoms had gone away, but it is still acting in the same manner with the replacement bottom case.

Any ideas? SMC/PRAM reset and software update do not help, and it does this even when in safe boot.

Mac OS X (10.6.4)

Posted on Sep 27, 2010 10:56 AM

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averagedude

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Dec 24, 2010 1:12 AM in response to discounteggroll

I had this same issue. I had my machine apart (13 Macbook pro unibody) to troubleshoot a keyboard back-light issue. Tried to fix back-lighting issue and threw it all back together and when I fired up the laptop, this same issue you have mentioned surfaced. Bottom case off laptop works perfectly. Bottom case on laptop works slow, cpu fan on high, airport not working.

Worked on it for days with no change. I tried everything I could think of. I figured it was something to do with the grounding points on the logic board.

Well it wasn't the grounds I was thinking it was. What it ended up being was a connector was grounding out on the logic board when the bottom cover was put on. The connector is one of the connectors that runs to the LCD. And it plugs in to the right of the optical drive and to the left of the speaker connection on the logic board. It routes back to right side of the LCD.

On the connector there is a piece of foam. I think this foam acts as some kind of ground as well. This foam contacts the bottom case when the case is installed. Well I peeled back the piece of foam and placed a piece of electrical tape over the connector and then re-attached the foam on top of the electrical tape so the foam was not in direct contact with the metal connector.

With this done no more CPU fan on high, air port returned to normal, and everything is working perfectly. If you have replaced the logic board and are still having this issue try checking for a short somewhere. They are a pain to find so good luck. Hope this helps you or someone.

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