Customer stated that furnace was not coming on. Cycled system in heat and found code 3 “Pressure switch stuck open. Inspected inducer and flue assembly for obstructions, inspected pressure switch and tubing. Existing switch was universal improperly set. Replaced with OEM switch with same result. Tested new switch. Tested draft inducer with manometer and found inducer not pulling adequate draft. Further inspection found cracked heat exchanger. Provided estimates for system replacement.