My Mac won’t turn on: what to check before bringing it in

First things first: if the Mac has been in liquid, stop here. Do not switch it on, do not charge it and do not try anything below. First aid for a laptop with liquid on it is at what to do with a MacBook that has had liquid spilled on it, and the order matters a great deal.

For everything else, one thing at a time. “It won’t turn on” is a symptom, not a diagnosis.

First, sharpen the symptom: these are five different faults

Watch what the machine does exactly when you press the button. Each answer leads somewhere different:

• Nothing at all. No noise, no warmth, no light. The fault is in the power circuit.
• There are signs of life but the screen stays black. That is not a power-up problem, it is an image problem.
• It starts and shuts down in a loop, or dies after a few seconds.
• It only runs with the charger plugged in and dies the moment you unplug it.
• It powers up but stops on a screen (question mark, frozen logo, prohibited sign). That is no longer start-up hardware, it is the system or the drive.

Note down which one is yours. It is the single piece of information that shortens the diagnosis most.

What happens inside when you press the button

Understanding the sequence helps, because it explains why some symptoms are mild and others are not.

The charger delivers voltage to the board. An input circuit accepts it and generates the first permanent power rails, the ones that are alive even with the machine switched off. The power button feeds nothing: it only signals the power manager, which then brings up the remaining voltages in a strict order and, if every one of them is correct, releases the processor to boot.

If a single one of those voltages is missing or shorted, the sequence stops there and the machine stays exactly as it was: dead, quiet and undramatic. Which is why a completely inert Mac does not mean a wrecked Mac. Very often it is a one-millimetre component on one particular rail.

Is it dead, or is it just not showing an image?

With the Mac closed and quiet, press the power button and look for this:

• Can you hear the fan, a click, the drive, anything at all?
• Does the machine feel warm around the keyboard after a minute?
• Does the keyboard backlight come on, or the caps lock light?
• In a dark room, shine a torch across the screen at an angle. If you can make out the desktop or the cursor, the image is there and what is missing is the backlight.
• Plug in an external monitor. If the image appears there, the machine boots perfectly and the problem is the screen or its cable.

If there are signs of life and no image, do not carry on with this guide: the path is a different one and it starts by ruling out the display cable and the backlight, not the power circuit.

Charger, cable and port: ruling them out properly

This is the dullest part and the one that turns out to be right most often. “I already tried another charger” does not count if that other charger is not a known good one.

• Use another charger of the same type and wattage, and if you can, swap cable and adapter separately so you know which one was failing.
• Plug it into a wall socket, not a questionable extension lead or a port on another machine.
• Leave it connected for a good while before trying to switch it on. A completely flat battery does not react instantly.
• With MagSafe, watch the LED: no light, a blinking light and a light that changes colour on its own are three different clues.
• Try every USB-C port. One port not charging while another does is common, and it already tells you the problem is that port rather than the whole board.
• Look inside the connector with a torch. USB-C ports pack lint into the bottom. With the machine off and a plastic tool (never metal), it comes out.

The full power-down

On Macs with Apple silicon the old SMC and NVRAM resets no longer exist. What does help is this:

1. Hold the power button for ten seconds, until it shuts down completely.
2. Disconnect the charger.
3. Wait thirty seconds.
4. Reconnect and switch on.

On Intel Macs the SMC reset still makes sense, and it varies by model, as does the NVRAM reset by holding Option + Command + P + R at start-up.

None of this fixes a physical fault, but it does unstick the power manager when it has hung, which happens more often than you’d think.

The swollen battery: the sign people ignore

If the trackpad has stopped clicking, if the lid no longer closes flush or if the machine rocks on the desk, the battery is very probably swollen.

What happens inside: the electrolyte in an aged lithium cell breaks down and produces gas. The cell inflates, pushes the trackpad up from below and the case out from within, and in advanced cases it goes as far as stressing the board or splitting the display cable. On top of that the system disconnects the battery for safety, and from then on the machine only runs plugged in, or does not start at all.

Stop charging it, do not carry it squeezed into a backpack, and get it looked at. It is a routine repair; what gets expensive is waiting until it deforms the case.

What not to do

• Pressing the power button over and over. If there is a short on one rail, every attempt feeds current into it and can spread the damage into healthy areas.
• Charging it with a swollen battery.
• Opening it yourself without disconnecting the battery first. A screwdriver and a powered board is the fastest way to turn a small fault into a large one.
• Restoring the machine in DFU mode. In that tool, “revive” preserves your data and “restore” wipes the machine completely. If there is anything inside without a backup, this is the most destructive thing you can do.
• Leaving it “being tried” in three different places. Every attempt changes the starting point, and the story has to be reconstructed before anyone touches anything.

When it is none of the above

If you have got this far with nothing to show for it, the fault is usually on the logic board: the charging circuit, the power management chip, an open coil or a short on one of the supply rails. A classic is the USB-C ports, which take voltage spikes and protect the board by destroying themselves.

That is not diagnosed by trying parts: it is measured. The board goes under the microscope, cold current draw is measured, and the failing rail is followed to the specific component. It is what we do in MacBook and iMac repair and in the microsoldering lab. Most repair services, not working at component level, can only offer you a whole replacement board, which usually costs close to what the machine is worth. If what you have on the desk is a Windows laptop, the route is similar but the details differ and they are at a laptop showing no signs of life.

That’s where the awkward conversation turns up: on a Mac that’s a fair few years old, if the board quote gets close to what the machine is worth second-hand, we’ll tell you with the numbers in front of us. We’d rather lose the job than charge you for it knowing it doesn’t add up, and what moves the price of each fault is set out on the prices page.

And if there is work inside with no backup

Say so the moment you walk in, ahead of anything else. On Macs with Apple silicon the storage is soldered and encrypted alongside the processor, so there is no pulling the drive and reading it elsewhere: the only route is repairing that board just enough to boot once. That changes the order of the entire job, and it is set out on data recovery.

We look at the machine, measure it and tell you what it has and what it costs before you authorise anything. The process end to end is on how the process works, the rest of the workshop guides come off the same bench, and if you’d rather start by telling us what exactly happens when you press the button, write to us.