"How can I test an infrared key fob?"This is another question which comes up quite frequently on forums when people are having issues syncing second hand key fobs or re-syncing them after buying new batteries. There's a simple check you can do which takes just 10 seconds and could avoid a lot of head scratching when you're trying to figure out why it won't seem to sync.
Scroll down to watch the video.
All that is needed to test your infrared key fob is a device with a digital camera and a screen which you can "look through" to see the infrared LED light up. Infrared light is normally invisible to the human eye but by some miracle of science we can view it through a screen (perhaps someone would care to tell us how this works in the comments?). In this video we used a cheapy digital compact camera but you can use smart phones, tablets, webcams, anything really.
Clearly if the infrared LED on the front of the key fob doesn't light up then you have a problem. Double check the batteries are the correct ones for the key fob and if their age is unknown, buy a new set.