If you turn the thermostat to the fan on position, does the fan come on?JACUSTOMER-bnh4gz65- :I think it's the fan I hear that comes on, when I move the thermostat up. I can see in the thermostat that the system indicator is on.M Oglesby :Do you have a Fan auto or On switch on your thermostat?JACUSTOMER-bnh4gz65- :Yes, it set to AutoM Oglesby :Set it to the on position and tell me if the fan comes on or not?JACUSTOMER-bnh4gz65- :The fan did not come on in the On position.The furnace just came on for few seconds when it was in the On position, but there was no air coming out from the register.The furnace just cam back on for few seconds again but still no air coming out from the register.The furnace just cam back on for few seconds again but still no air coming out from the register.M Oglesby :This may be a flame sensor issue.The flame sensor rod is a small thin steel rod that is straight or L shaped. It is located near the pilot igniter or in the path of the burner jets.Locate it, remove it, and clean it with a piece of emery cloth or sandpaper very good.JACUSTOMER-bnh4gz65- :I am still trying to locate this.M Oglesby :How old is this furnace and what is the name brand of it?JACUSTOMER-bnh4gz65- :About 9 yrs. old, Armstrong G1N80ARM Oglesby :Did you find the flame sensor rod?JACUSTOMER-bnh4gz65- :Yes, looks like it will take time for me to remove.I just removed, cleaned, and reinstalled the flame sensor rod. Tested the furnace and it is still not working.It is the same as before, I noticed that the furnace runs for 30 seconds and stop.M Oglesby :Have you checked the batteries in the thermostat if it uses any?If so, I want you to remove the thermostat cover and you should see a R terminal and a W terminal. Remove the R and the W wires and twist them together. Let me know if the furnace will come on and stay on or not.JACUSTOMER-bnh4gz65- :The batteries are fine, but I went ahead changed them with new ones. I connected R and W wires, the furnace runs for 30 seconds and stop. The fan turns on also and stop. I observed that the ignitor did not ignite, and I think it is the ignition control (where the gas pipe pass) has a blinking light on top. It blinks continuously when the furnace is running, and then it blinks 3 times every 3 seconds when the furnace stop.M Oglesby :Remove the door panels and find out what the 3 flash LED troubleshooting code is indicating.JACUSTOMER-bnh4gz65- :"Pressure switch open. Should be close." How do I close it?M Oglesby :The inducer fan motor is located inside the furnace cabinet and is connected to the flue pipes. It has a rubber hose attached to it that connects to a round pressure switch. Locate what I just described and let me know when you find it.Remove the rubber hose and blow through it to make sure it is clear. Also inspect it for breaks or tares. Then use a paper clip to clean out the connection at the inducer fan motor very very good applying force if necessary. Make sure the paper clip goes all the way through to the fan blades. Replace the hose then call for heat.Let me know what happens.JACUSTOMER-bnh4gz65- :It's is working now. Thanks a lot!