I have brand new goodman furnace, AC part works fine, but when I turn it on heat the draft inducer motor never starts. I checked there is no power coming to it from the control board.

Jump r and w on the control board and let me know what happens. Make sure the blower compartment safety switch is pushed in while running this test, otherwise you will not have power to the control board.

After I jump r and w the red light flashes 3 times, indicating pressure switch failure. But the draft inducer fan never starts so I am thinking its not pressure switch problem.

If a pressure switch is stuck closed, it will not allow the draft induce to start. Try disconnecting both wires from both pressure switches and let me know what happens.. If this is a brand new furnace, I really think you need to have the installer back to trouble shoot the furance. Doing work on the furnace yourself will void warranty. If you installed the furnace yourself, then warranty is already void, in which case I will try to help as best I can.

I thought there was only one pressure switch, This is a GMS8 Single stage furnace, I Tried disconnecting wires from one pressure switch no change, blower did not start.

Sorry, your correct. Only one ps on your unit. Now, bear with me here. There are anywhere from one to three flame rollout switches on you unit Located directly above the burner assembly. They are small switches with a small button in between two wire connections. Press on the small button and if you feel or hear a small click, then the limit was tripped and the click reset it. One step at a time here, as its hard for me to diagnose without having my hands on the unit.

I will try the rollout switches first thing tomorrow. This furnace is in the rental unit so I can work on it only during day hours. Do you have any suggestions on what else to try if its not the rollout switch.

I finally got this furnace to work. What happened was that some water got to the control board and made it malfunction. Had to replace whole board ($60 at local goodman distributor), and a pressure switch which was also bad ($14)

Glad you got it fixed, and thanks for the update.