Situation: I am a A/C and heat techinician and I have a problem with a Bryant gas heater. The heater has a Circuit/Ignition Board, HK42FZ009. The LED on the board blinked two times, paused and blinked three more times. The LED continue to blink when the system is not calling for heat. The Customer stated that the LED had blinked all summer. I disconnected the heat circuit between the thremostat and the board, and the LED still blinks. In the heat mode none of the heat system will power up. The A/C and the inside fan works. Question,: What is wrong with the heat system?

Usually a 23 means a pressure swich problem. Many times that is something restricting the exhaust so check the discharge pipe outside first. You said the heat system will power up? Does that mean it is working when this code is present?