MacBook Air, coffee+heat. Almost working.

mrelwood

I purchased a MacBook Air 13" mid 2013 that had coffee spilled on and dried in a sauna (heat room). I have cleaned the spills, replaced the screen backing sheets and the keyboard keys. The laptop is now usable but not 100% ok. The battery showed no capacity, had the X logo at the top bar, and wasn't charging so I removed it and am now using a power adapter secured by tape. The strange thing is the power adapter light is solid amber. I think it should be green when no battery is present. SMC and NVRAM have been reset a few times, and it is running the latest OS 10.9.5.

The other problem is that the CPU frequency doesn't get above 0.80GHz (1.3GHz model), and the fan doesn't speed up from the base 1200 rpm under a multi-core stress test. The CPU temperature doesn't get above 57°C.

Could the SMC chip be fried, or does the OSX have a CPU clock frequency limit when no battery is present?

John

Thanks for the post!

I've only worked on a few 13" Airs, so I don't have tips and tricks specific to that laptop, but generally it sounds like you're probably dealing with a logic board that has gotten fried to the extent that it can no longer charge or recognize a battery, and I'd expect that your battery is probably good. An X, or battery numbers that show the computer is not recognizing a battery, tends to confirm a board that has damage. This situation is common with liquid spills, and if you've removed all the visible corrosion and still have the battery non-recognition issue, there's not much to do but start swapping parts.

An amber light when no battery is connected is further evidence of board damage, and specifically damage to the power subsystem of the board. One thing I would suggest is to disconnect the DC-in module (the smallish daughterboard next to the logic board which contains the DC-in jack), and let it sit overnight removed from power. This is because, as a power-related component, DC-ins often have the ability to contract a "bad charge", and when this "bad charge" dissipates, they sometimes act differently, i.e. go back to a green light, etc. It's probably unlikely, but worth trying, and I've seen lots of DC-ins "reset" themselves in this manner. If that doesn't help, I would start by replacing the DC-in module (it might be technically called something else in the case of Airs, but I don't know the official Apple terminology), since it is power-related and often the culprit with charging issues, and cheaper than replacing the board. Hopefully the liquid spill affected it and not the main logic board.

Unfortunately I don't have the knowledge to answer your more technical questions. My approach is always to replace parts rather than take measurements, because as you're experiencing, once you have the measurements it then becomes and issue of determining what those measurements mean (if anything), and then what to do about it. Not that that isn't valid, but I find replacing parts to be an easier and more clear cut method of discovering what's wrong.

Thanks and let me know how it goes!

John

mrelwood

Oh my, thank you so much John! After your explanation a malfunctioning power board indeed could cause the issues. I wasn't hunting for specific MHz numbers, but as the Air was showing a disturbing lack of performance, I wanted to find out what's causing the issue. Thinking of it now, I feel a bit stupid not removing the power board as I was cleaning the spills, as there probably are stains underneath the board.

I'll try to dig in again in the near future, and will definitely post any results.

Thank you again for the very valuable help!

John

Sounds great, and good luck! It's easy to forget that there can be corrosion on top of the board -- I do it all the time. I wonder if all the problems might be resolved by replacing the DC-in board....

Thanks, and let me know how it goes!

John

mrelwood

So I disassembled both the power board and the main board. There were substantial stains on the main board, but the power board was clean. Assembled, reset SMC, reset NVRAM and tested, but the behavior remained unchanged. Fueled by slight frustration I put in a new battery, fearing that it wouldn't work any better than it did with the original battery.

To my pleasing surprise it now works completely! The CPU clock frequency tops at 2.3GHz (turbo boost from the spec'd 1.3GHz), CPU wattage jumps from the previous 4W to 12W, and the temps rise up to 94•C after two minutes of full load (used to max out at 50•C). Didn't yet run Geekbench, but as the OS is now more responsive and all seems fine, I'm sure it will get decent scores.

So, it seems there is a "limp mode" when no battery is detected. Atleast on the MBA 1466 13" 2013.

Someday I'll attack the display assembly again and hopefully manage to do a clean reinstall without breaking the screen. THEN the Air will be literally as good as new, both in and out.

John

Wow, that's great news! Usually when a battery stops working after liquid damage happens it ends up being the board or the power module, but I guess this was an usual case. It's still good that you cleaned up the corrosion, even though it doesn't seem to have been the cause -- corrosion can continue to eat through a board, so it might have caused problems later if it hadn't been cleaned up.

Anyway, congrats!

John