By Gareth Downes‑Powell | Updated March 24, 2022

Infrared LEDs (IR LEDs) power many remote‑control systems, from TVs to garage door openers. Because IR light is invisible to the naked eye, diagnosing a faulty LED can be tricky. The trick is to use a digital video camera or a smartphone capable of capturing infrared, which will display the LED as a purple glow on the screen.

Step 1: Verify Power

Insert fresh batteries into the device. This rules out low voltage and lets you focus on the LED itself.

Step 2: Prepare the Camera

Turn on your digital video camera, or switch your smartphone to video mode.

Step 3: Locate the LED

Point the camera at the LED area—usually the black, shiny plastic cover on a remote control.

Step 4: Test the LED

Press any button on the remote. A functioning IR LED will appear as a purple glow in the camera’s viewfinder.

TL;DR

If the LED fails to light, replace it. Replacement LEDs are widely available at electronics stores or online.