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The April 2014 update of Apple's 13" MacBook Air features refreshed dual-core i5 and i7 processors, plus slightly increased battery performance.

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MacBook Air 2014 will not start with battery connected but runs fine w

This is a i7 1.7GHz, 8gb RAM and 250gb SSD. Suddenly it would not start up. I suspected the I/O Board since the charging light was only sometimes on. So I replaced the I/O Board and it started up. The problem now is:

  • Will not start when battery is connected even if charger is attached
  • Starts fine if I disconnect the battery and start from charger
  • Connect the battery and the battery charges fine
  • Disconnect charger and runs fine off of battery
  • Restart works fine from battery only
  • Wakes from sleep from battery only
  • Shut down and the issue is back, will not start and have to disconnect battery to start from charger

What I have tried:

  • Tested another working I/O Board
  • Reset PRAM and SMC
  • Run Apple Diagnostic - passed all tests
  • Tested with another working battery
  • Tried to jump start from start pads behind the WIFI board

Is there some kind of chip that triggers from the battery that is bad? Any suggestions?

Here is the trackpad cable

Block Image

Update (07/19/2018)

No, @danj I really don't know what is bad here. I have tested with a working I/O Board cable but with no better luck. I can start with shortening the pads but only when the charger is connected. Just randomly I can start with the keyboard power key but only if charger is connected. I looked at the I/O cable connector on the logic board and it looks different from another (2013) MBAir in the way that on one side there are 2 pins less. Not easy to explain but I could not get a good picture of it. Could this be any issue? I measured the the start pads. 3.41 V without the charger connected and 3.42 V when the charger is connected. Not big difference but a differnce. I don't understand the logic, I am thinking this is some sort of grounding problem. Without proper ground there will not be a shorting? But the grounding is obviously not in the trackpad and its cable. When the charger is attached there seems to be grounding since it starts then. Is this a path to investigate?

Answer this question I have this problem too

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I'm suspecting the keyboard. Since you have a second swap out the logic board.

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I just tested with a new keyboard and that did not help. But I did not install it with screws, just attached the cable. Will that give bad terminus? Then it would be easier to move the logic board to another MBA that works. Ah, so much work. But I am on some track that might succeed.

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1 Answer

Most Helpful Answer

The trackpad is the terminus of the keyboard cable and then both the keyboard & trackpad signals travel over the trackpad cable.

What I often find is corrosion on the trackpad and/or the cable. Pull the trackpad out and do a good inspection looking for corrosion. MacBook Air 13" Early 2014 Trackpad Replacement You likely need to replace the trackpad and one or both cables.

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@danj you really are onto something. Never thought of the shared connection for the track pad and the keyboard.

But then I wonder how that would relate to the battery plugged in. Looking for the logic here. Sure enough when I disconnect the trackpad I’m able to start the system shortening the power pads, only once from the keyboard.

I have added a picture of the cable. Not easy to get a good picture. But the cable seems OK on the trackpad side. Can you tell anything from the picture?

The Air has had no water damage so wonder how this can happen. I will try to get another trackpad and test first only the cable and then the trackpad.

Do you think the keyboard also could have an issue?

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The power switch on the keyboard it dependent on a voltage difference between the two sides of the switch ground on one side and 3.42V on the other (if I remember correctly). When you ground the line it goes into a low state so SMC powers up the system (measure the power pad voltage with and without the trackpad connected). So if you have corrosion thats leaking the voltage then it doesn't toggle as its' not in the needed state.

Well, it's likely has some liquid damage. I'm suspecting if you asked the person who owns the system they use a spray cleaner (Windex or such) they spray the uppercase without thinking where the cleaner will creep into. Which is why its important to spray the cloth not the equipment.

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## UPDATE ## I tried to change the trackpad and cable but that did not help. I tried the trackpad and cable on another MacBook Air (2013) and it worked fine so the problem can't be the trackpad/cable. Now when I have the charger connected (battery is plugged in) I can start with the keyboard and then remove the charger. So the Air runs fine from battery but does not recognize the startup key press.

Is the voltage difference you wrote about also present on the battery connector? Is there one line just for startup? Could there be corrosion or bad contact there?

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The battery is merely the power source for everything, then its pushed through voltage dividers the 3.42 is after the battery through a divider. The keyboard is using this lower voltage (as well as the on/off switch and the power pads).

So I think you know whats bad here... If the logic board is able to power on via the power pads without the trackpad cable connected we know the logic board is good, As you tested the trackpad cable and trackpad in another system I think we can agree these parts are good so whats next up the food chain?

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@danj I am not really sure whats bad here. I tried now to even replace the the I/O cable with no better luck. I was able to start (a few times) from the keyboard with a charger plugged in. Now I can only start shortening the pads and only with the charger connected. This seems like a grounding issue? Surely there is better grounding somewhere when the charger is connected. So I have tested the trackpad and cable in another MBA but that was a 2013. Should be the same? Guess I have not tried a completely new trackpad, although I have tested the trackpad and cable in the 2013 MBA and it worked fine. Just thought about that since I now am not able to start at all from the keyboard.

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