Model 340AAV condensing gas furnace was installed in 2008. Tested the unit by turning off the unit and gas. Next I set the thermostat just a few degrees above the house temperature, turned the gas valve to the on position and then turned on the heater unit. The burners started immediately and began the cycle process. Ater 4 minutes the system kicked off. The fan never started. The ac works fine and the fan is working. Checked the filter and the filter is clean.

Return code suggested the air intake was blocked. The service man cut the intake pipe and discovered birds blocking the air intake. He said this is a common problem during the first cold spell. He reattached the air intake pipe and the unit works fine.