ARCHIVED: What should I do if my monitor display flickers or wavers?

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Note: The following information applies to cathode ray tube (CRT) monitors. If an LCD (flat panel) monitor flickers or wavers, even under the conditions below, it may be defective.

The most common cause of a flickering monitor is a low refresh rate. The refresh rate controls how many times per second the monitor redraws, or refreshes, the screen. The default setting video cards support is 60Hz. At this setting, it is very easy to notice lines or flickering in your monitor. A 75Hz setting will cause little or no flickering, but to make viewing easiest on your eyes, UITS recommends a refresh rate of 85Hz or 100Hz, depending on what your monitor supports. To change your refresh rate, follow the appropriate instructions below:

Setting the refresh rate


  1. From the desktop, right-click and choose Properties.
  2. Click the Settings tab. For Windows NT, skip to the last step.
  3. Click Advanced.... Click Monitor (Windows 2000 and XP) or Adaptor (Windows 95, 98, and Me).
  4. Change the refresh rate as desired. If you set it too high, your monitor may go blank or display a garbled screen. If this happens, don't change anything. Windows will restore your previous settings after about 15 seconds.

    Note: If the option for changing your refresh rate is grayed out or not listed, then either the driver for the video card is not properly installed, or the driver does not allow this change. Check the manual for your video card or contact your computer manufacturer. This option may also gray out if you have an LCD flat panel monitor, as the refresh rate should not be changed.

Mac OS X

  1. From the Apple menu, select System Preferences....
  2. From the View menu, select Displays.
  3. Click the Display tab. From the Refresh Rate drop-down menu, select your desired setting. The change will take effect immediately. You may need to experiment to find the best setting for your computer.

Checking for interference

Proximity to the following items can also cause monitors to display improperly:

  • Electronic devices, such as other monitors, speakers, televisions, and refrigerators. Make sure your monitor is not sitting too close to or sharing a socket with these devices.

    Note: Sharing a socket with a refrigerator in particular can cause problems. When the refrigerator is cooling, it draws more current, which can cause sudden dimming or wavering of your monitor display.

  • Magnets, such as the magnet at the base of a speaker cone. Standard computer speakers are shielded to prevent damage to monitors, hard drives, and other computer components, but larger stereo component speakers are not. If a large speaker is close to a monitor, it increases the possibility of display impairment or damage.
  • Fluorescent lighting tubes. Fluorescent light modulates with the frequency of the alternating current that powers it. This modulation, when close to the top of a monitor, will cause the display to waver. Move or turn off any fluorescent lights near your monitor.

If these methods don't fix the problem, your monitor may be going bad. If your monitor is still under warranty, contact the manufacturer or the vendor from which it was purchased. If the warranty has expired, contact a monitor repair service.

This is document adjt in the Knowledge Base.
Last modified on 2018-01-18 10:29:41.