If your furnace status LED is blinking a steady single blink this usually means the system is either in stand by mode or is receiving a call for heating or cooling. If the LED light is blinking rapidly more than once and then pauses and does more this usually indicates the furnace has an issue and some sort of failure or a safety device has tripped. The codes can be difficult to read unless you read them all the time but they normally refer to two specific numbers that correspond to a troubleshooting chart in the manufacturer manual or sometimes right on a sticker on the furnace door. Each code usually tells the technician what to look for on the system and in most cases there can be more than one thing to check. Find more frequently asked questions on our wesite asi-heating-airconditioning.com