The iMac screen is the biggest and most expensive part of your iMac. If lines appear, the screen stays black while you can hear the iMac, you see marks or dust behind the glass, or the glass is cracked, you want to know what is going on and whether it can be repaired. This article covers the most common iMac screen problems, what you can test yourself and what a screen repair involves.
Blue Apple repairs iMacs and MacBooks in Amsterdam, including when the screen is the problem.
Test first: the screen or something else?
- Take a screenshot with Shift + Command + 3 and view it on another device. If the lines are not in the screenshot, the problem is in the screen or cable. If they are, the graphics chip or software is more likely.
- Connect an external display, if your iMac supports it. If the picture is fine there, the built-in screen is to blame.
- Look in Recovery mode or at the startup screen: if the lines are there before macOS loads, it is hardware.
Lines
Vertical or horizontal lines, often in one colour, usually come from the panel itself or from the cable connecting the screen to the logic board. On the 27 inch Retina iMacs you sometimes see lines that slowly increase. If the lines come and go when you gently touch the iMac or when it warms up, that often points to the cable or connector.
Black screen, but the iMac runs
Do you hear the iMac start and does Caps Lock respond, but you see nothing? Shine a torch at an angle on the screen. If you see a faint picture, the backlight is broken. If you see nothing, it may be the panel, the cable or the graphics chip. Also read iMac will not start up.
Marks, dust and discolouration
- Dust behind the glass: on older 27 inch iMacs dust enters through the ventilation between the glass and the panel. You see it as grey smudges, especially at the top.
- Light or dark spots can come from pressure on the screen or wear of the backlight.
- A yellow or pink tint on one side: sometimes a panel problem.
Cracked glass
On an iMac the glass and screen are attached to the housing with adhesive strips. On newer models glass and panel are one unit, so with cracked glass the whole screen must be replaced. During a repair the adhesive is cut and new adhesive strips are fitted afterwards.
Taking a screenshot on an iMac
It works the same as on a MacBook: Shift + Command + 3 for the whole screen, Shift + Command + 4 for a part, Shift + Command + 5 for all options, including screen recording. See making a screen recording.
iMac as a second screen
Want to use your iMac as a monitor for another computer? That only works on certain older models or via AirPlay. We are writing a separate article about it.
What we do at Blue Apple in Amsterdam
We test whether the problem is in the panel, cable, backlight or graphics chip, and then tell you what the repair costs before we start. Carry an iMac lying down with the screen facing up; if that is not possible, see our pickup and delivery service. More about how we work: Mac and MacBook repair in Amsterdam.
Frequently asked questions
Can just the glass of an iMac be replaced?
On older models with separate glass, sometimes. On newer models glass and panel are one part.
Do lines go away by themselves?
Usually not. They often increase, especially with a loose or damaged cable.
Can I remove dust behind the glass myself?
That requires taking the screen off and fitting new adhesive. We do not recommend it without experience.
