iMac Screen Horizontal Lines Fix

Persistent horizontal lines on an iMac display almost always point to one of three failures. 1) LCD T-CON (timing control) board: lines that appear after warmup but disappear after a cold restart suggest the T-CON is overheating. 2) GPU failure: 2011 iMacs (Radeon HD 6970M / 6790M) had a notorious solder-joint failure causing horizontal banding - Apple's repair program ended years ago but the fix is a GPU reflow or replacement. 3) Display cable: lines that change when you press on the screen edge mean the LVDS ribbon is loose or kinked. To diagnose: connect an external monitor (works on 2011-2014 iMacs via Target Display Mode; later iMacs need a USB-C/HDMI adapter).

If the external is clean, the iMac's logic board and GPU are fine - it's a panel/cable issue. We replace iMac LCDs and reflow GPUs at our Dubai workshop. Bring the iMac in for a free diagnosis.

Laptop panels fail differently; our blurry screen fix for the M1 MacBook Pro 16 covers the scaling and panel checks.

Lines caused by a failing GPU are a board-level fault, handled under iMac logic board repair.

If yours is the 24-inch M3 model, the parts and diagnosis differ from the Intel machines above; see iMac M3 repair.

The 2011 27-inch iMac is the one we are most careful to be honest about. A reflow of the graphics card holds for a few months, sometimes longer, and then the lines come back; a replacement card lasts. We tell people that before they spend anything, because a cheap reflow that fails in August is money gone twice. Dust is a factor on every model: an iMac that has sat in a Dubai office for years has the rear vents and the fan packed, the panel runs hotter than it should, and heat is what brings the lines out.

On the slim models, pressing on the glass to test is a bad idea; the panel is bonded to the glass and pressure can add a new fault to the one you are diagnosing. Photograph it instead.