Mac won't start — every cause and what to do
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Quick answer
When a Mac won't start, the cause is almost always one of 15 typical scenarios. Work through them systematically: charger, power button, screen, reset. If nothing works, it's hardware — and we can repair most of it for far less than the price of a new Mac.
Alle spørgsmål
Why won't my Mac power on?
First: check whether the charger works (LED on MagSafe, try a known-working charger). Hold the power button for 10 seconds for a hard reset. Try an SMC reset (Intel) or hold the power button for 10 seconds (Apple Silicon). If nothing works, it's typically the power-management IC, the battery or the logic board — contact us for diagnosis.
Why doesn't my Mac respond to the power button?
The most common cause is that the battery is fully discharged and the logic board can't wake itself, even with the charger plugged in. Leave the MacBook on the charger for 15 minutes without pressing anything. If still nothing, it's either a faulty power button, a faulty SMC chip or a shorted component on the logic board.
Why is the screen black when I turn on my Mac?
If you can hear the Mac starting (fans, startup chime) but the screen is black, the fault is typically in one of three places: 1) the LCD panel itself, 2) the flex cable between display and logic board, or 3) the display controller / GPU on the logic board. Plug in an external display via USB-C: if external works, it's either the panel, the flex cable or the internal display path on the logic board — all three are repairable with us. If external doesn't work either, it's definitely a logic board fault. Diagnosis tells us which part.
Why does my Mac start and then shut off again?
Restart loops are typically caused by: 1) a faulty or expanded battery that can't deliver stable voltage, 2) corrupt firmware after a failed update (try a DFU flash), 3) faulty RAM or SSD, or 4) overheating triggering the safety cutoff. We can diagnose it in 30-60 minutes.
Why won't my Mac start after an update?
The update was likely interrupted or corrupted. Try: 1) hold the power button for 10 seconds for a hard shutdown. 2) Boot in Safe Mode (hold Shift at startup). 3) Boot in Recovery Mode (Cmd+R / hold the power button on Apple Silicon) → 'Reinstall macOS'. Reinstallation does NOT delete data.
Why won't my Mac start after a battery replacement?
If you replaced the battery yourself and it won't start: check that the battery cable is correctly seated and that an SMC reset has been performed. If you used a third-party battery without Apple's authentication chip, macOS may reject it. We use approved batteries that play nicely with Apple's software.
Why won't my Mac start after liquid damage?
Even small amounts of liquid can short the logic board. NEVER turn on a Mac that's had liquid spilled on it before it has been opened and cleaned. Every hour counts — corrosion eats into the copper traces. Send it to us immediately; ultrasonic cleaning can usually save the MacBook if it's done within 24-48 hours.
Why won't my Mac start after a reset?
If you've run an SMC or NVRAM reset and the Mac is still dead, it's not a software problem. Resets can't damage hardware — they just clear small settings. The lack of startup is hardware: battery, charging circuit or logic board. Get it diagnosed with us.
Why won't my Mac start after sleep?
If the Mac won't wake from sleep: 1) press a key and wait 10 seconds. 2) If nothing, hold the power button for 10 seconds for a hard shutdown, then start it. 3) If the problem keeps happening, it's typically the battery (can't hold standby current) or a fault in the sleep-wake firmware. An SMC reset often solves the latter.
Why won't my Mac start after running flat?
A fully discharged lithium battery enters 'deep discharge protection' and can need 15-30 minutes on the charger before it accepts current again. Leave it on the charger without doing anything for 30 minutes. If it still won't power on, the battery may be permanently damaged and need replacing.
Why won't my Mac start after overheating?
Overheating can trigger a thermal cutoff that powers the Mac off. Let it cool for 30 minutes, then try starting it. If the problem keeps happening, the cooling system is clogged (dust) or the thermal paste has dried out — a standard MACMO 'tune-up' (cleaning + new thermal paste) solves it for DKK 800-1,500.
Why won't my Mac start after an SMC reset?
SMC resets address power, battery and thermal management. If your Mac still won't start after a reset, the fault isn't in the SMC domain — it's likely the battery, charging circuit or logic board. Note that Apple Silicon (M1+) no longer has an SMC; a hard restart (10 seconds on the power button) is the closest equivalent.
Why won't my Mac start after an NVRAM reset?
NVRAM stores display, audio and startup settings. Resetting it only solves problems in those domains. If your Mac doesn't start after an NVRAM reset, it's hardware (typically SSD detection, RAM or the logic board). Get it diagnosed with us.
Why won't my Mac start after replacing the SSD?
First check that the SSD is correctly seated (on models where that's possible). Boot into Recovery Mode and use 'Reinstall macOS' to install the system on the new SSD. On models with a T2 chip or Apple Silicon, the SSD is cryptographically tied to the logic board — a third-party SSD can't simply replace it.
Why won't my Mac start after a RAM upgrade?
If your Mac beeps three times at startup, the RAM isn't seated correctly or isn't compatible. Check: 1) the RAM modules are clicked all the way in. 2) They're the correct speed and type for your Mac. 3) On Apple Silicon, RAM CANNOT be upgraded — it's soldered. Note that most 2014+ Macs have soldered RAM.