I was called to a home to check the AC and heating system. I ran the unit and AC and checked for a temperature split. I checked amps and ohms on both units. I checked the wiring and pressures on the outside unit. I also did a radon test.
Customer stated unit was blowing out cold air. Checked operation and system ran. Checked flame sensor and found it dirty. Cleaned buildup off of flame sensor. Found flue pipe leaking into furnace causing rust. Fixed flue pipe. System ran. Let customer know to get carbon monoxide detector