I've got the old 3 blinks, plus one long blink which seems to translate to Code 31 on my Carrier Infinity. This must be a very minor issue because it usually fixes itself before I can do anything, but I'm going to ask here anyway. According to the manual, this means:
Code 31: HIGH-HEAT PRESSURE SWITCH OR RELAY DID NOT CLOSE, OR RE-OPENED. indicates the high-heat pressure switch input failed to close or opened during high-heat. Control relay may be defective or gas valve is miswired. Refer to status code # 32.
Code 32: LOW-HEAT PRESSURE SWITCH DID NOT CLOSE, OR REOPENED. Indicates the low-heat pressure switch input failed to close on a call for low-heat, or opened during low-heat. If opens during 5 minutes after ignition the next heating cycle will be restricted to high-heat. Check for: proper vent sizing, excessive wind, plugged condensate drain, low inlet gas pressure (of LGPS used), restricted combustion air supply, improper pressure switch wiring, water in vent piping or possible sagging pipe, disconnected or obstructed pressure tubing, failed or "out of calibration" pressure switches.
So, what's the most likely fix it checks for this?
Help is greatly appreciated!