The brain of most modern furnace electronic ignition systems uses an integrated circuit board to control many complex processes. These integrated controllers also perform self-diagnostics providing codes to troubleshoot operational problems. The integrated circuits continuously monitor the furnace's operation and the operation of the integrated control module itself. If a failure occurs, LED's can indicate a failure code. The codes are listed in the service manual and also likely on the furnace door.

You will often find the control board in the blower compartment of the furnace with a 3-5 Amp fuse to protect the board from a short.

Integrated controllers are always used on higher efficiency furnaces that rely on many sophisticated design features to reach their high AFUE ratings of over 90%. However, they still provide the same basic function as the older technology from the non-integrated electronic control module. Simply put, the circuit boards control sequences of operation for the furnace