If you ever run across a Coleman gas furnace that short cycles and shuts off soon after ignition, check for the proper exhaust stack before replacing the circuit board or other ignition components. Sometimes when the furnace was replaced the installing HVAC contractor may have neglected to upgrade the exhaust stack on top of the roof as well. When this happens the furnace will not have the proper combustion air and will run poorly or not at all. The image shows what the upgraded furnace stack should look like.