MacBook Air a1370 only runs on the charger

[crea2k]

Bit of an odd one here, the customer Changed the battery because it would only run on the charger, but it appears to not be charging the battery as the MagSafe light isn't even on at all when it's plugged in, but the Mac will power on just fine. It's just if you pull the cable the Mac instantly turns off. I don't have a spare charger to test it with but wasn't sure if this was a common problem anyone that works on macs had seen before ?.
other than the backlight circuit I don't know that much about them to be honest.

[crea2k]

Customer said it worked on the new battery until it went flat, then will only run on the cable again. So apppears to be a charging problem.

[AaronH]

No light on the magsafe is most often a problem with the onewire circuit. Louis Rossmann has tons of videos on this which explain it way better than I could try to.

[crea2k]

Cool thanks I shall take a look

[crea2k]

Does this apply to no light at all ?, as I see he mentions 'no green light', but wasn't sure if that was still with orange light,as there is no light at all.

[Jessa_the_Professa]

Do you have a green light when the charger is plugged in? And just no orange light? Does it show the battery percentage or just an X? Or do you have no charger green light or any light at all on the Charger?

[crea2k]

There is no light on the charger at all, not green or orange, just dead, but we know the charger is outputting some kind of current as it powers the mac, but the light on the connector near where it plugs in is dead to the world. Iv seen them with bad batteries where the light wont change colour, but on this one the light doesnt even come on. Il have a look at it and see what the battery percentage says. I do know that when the customer fitted the battery the mac would run happily on just the battery, until it ran flat, now it just runs on the power cable again as before.

[Jessa_the_Professa]

That starts with rule number one—get a known good charger and look at the port to make sure it is getting a good connection. And known good battery. Bad chargers themselves are the most common problem. Report back with whether the device can see the battery at all. I would not expect a good charger that can be recognized by the device and allowed to send charger voltage into the device to power it on to not have a green light at all. So I would expect this to be a bad charger until it is a more classic presentation: no charger green light AND device doesn’t boot from charger OR charger green light and device boots from charger but doesn’t change to orange and charge the battery. This is outside my experience base since we rarely fix MacBooks but that is where I would start.

[crea2k]

Ok thanks, il have to order a charger in as I dont generally see any macbook board repairs, just software, and batteries and the odd hard drive, so il try another charger as a first port of call. This post was just fishing for ideas as I didnt know if someone was going to say "oh thats the old classic such and such that always die", so il check the obvious things now first

[larossmann]

Is the DC in cable corroded?

Is PP3V42_G3H making its way over to the DC in board? Look for these two chips on the DC in board. Video here from 3:10 will explain. https://youtu.be/xj3y8IhDPOQ?t=192 On any other macbook from the same year like the 820-2850, 820-2915, 820-2879, 820-2936, etc, there are two pieces that control charger green light: U6900 and U6901. U6900 sits between the charger and the SMC(they need to talk in order for you to get a light). U6901 is what powers U6900 if all conditions are correct. These are not on the schematic for Macbook Airs because Macbook Airs do not have these two components on the main logic board, Macbook Airs put these two components on the DC in board.

Here is U6901 on top, and U6901 on the bottom, on a macbook air dc in board. See attached picture.



A bad dc in board or dc in board cable or bad dc in board connector will prevent SMC_BC_ACOK and PP3V42_G3H from making it to the DC in board. U6900 talks to the charger and lets charger info through on, so bad cable/connector will also cause SYS_ONEWIRE from U6900 from talking to the SMC, which is needed.

Now it is possible your SMC is also wrecked altogether. If the SMC is wrecked it doesn't matter if your charger/dc in board/dc in cable are fine and all voltages are what they need to be, nothing will work. The SMC talks to the battery and also to the charger. Bad SMC means it won't green/orange light the charger and it won't see a battery.

The SMC, U4900, talks to the battery charger(U7000) and the battery. The battery charger(U7000) creates PPBUS_G3H which should be 8.16v. However, the SMC tells it to create 8.56v. So if the SMC is working and on and doing its job, you get 8.56 volts on PPBUS_G3H. If the SMC is destroyed or corroded you get 8.16 volts on PPBUS_G3H. What do you get on PPBUS_G3H, 8.56v or 8.16v?

[Jessa_the_Professa]

Louis--My understanding is that without 3v42 you can't get ppbusg3h and therefore could not get the thing the turn on. What he is describing is "It boots and runs just fine on DCin and will indefinitely until you pull charger out, AND he NEVER gets a green light or any light" To me that sounds impossible---if the device is recognizing and allowing the charger to power on the device, then it MUST be producing a charger green light--unless the problem is just between the very end of the sysonewire circuit back to the port where it just is open line after whatever is the last dude on the dcin board line between him and the actual pin on the charge port.

If that's the case, then I would expect this to really be a charger green light, no charger orange light and we can go from there. At this point, however I would think that following rule #1 would be the first step since as far as I can tell "Device powers on via DC, but I get no light" is an odd presentation.

[crea2k]

Iv got a new dc in board but still no good. Iv found those two components in the dc in board and tested for those voltages and they are all over the place, sometimes it's 3.5v other 1.5v etc. When you put the probes on the board after turning on the voltage increases slowly, so can't give a definitive voltage for either. When the fan spin stops after a few seconds the voltages start to fall back down slowly again. Iv tested both lines for shorts and neither is short.

[crea2k]

Thanks for the reply Louis much appreciated, I shall check voltages tomorrow when back in and post back.

[crea2k]

Ok so the new charger came today and has the same no light problem so il proceed to the next step and pull it apart and check voltages.

[Jessa_the_Professa]

What does it say by the battery icon? Does it show the battery and a percentage, or just an X?

[crea2k]

So this is what the dc in board looks like argh, what are the two components just behind the connector ?, as they look unhappy.

[Jessa_the_Professa]

As in the replaceable DC in board? That's part of rule #1--get a new one!

[crea2k]

Yer I realised last night it was replaceable as thought it was hard wired at first, but have ordered a new one now, so fingers crossed.