I arrived for a warranty no heat call from a system we removed the furnace and replaced the evaporator coil and cond And reinstalled the furnace. I inspected the system and found the pressure tube leading from the induced draft motor to the pressure switch to have come loose and preventing the furnace from cycling on. I reconnected the tube and cycled the furnace on at the system and from the thermostat and found the system to come on and run properly. I found some debris in the furnace blower compartment and the homeowner got his vacuum and I cleaned blower compartment out as well as the top of the water heater and furnace and floor of the utility closet. This system is running properly at this time.