I have a 6 years old Goodman furnace [GMH950703BXAG]. I keep getting the code 3 (3 FLASHES - Pressure Switch Stuck Closed). The exhaust motor kicks on, runs smoothly (no odd noises), but the furnace never gets flame and starts the blower motor. The pressure switch is labeled -0.95. Using a manometer, I measure -0.74 with the exhaust motor only running (no flame), if i bypass the pressure switch and light up the furnace, I measure -1.15 in-H20, the same pressure is measure on either side of the heater plate. When I bypassed the switch i watched the flames as the blower comes on to check for disturbances in the flame, no disturbance at all (to check for a potential heat exchanger crack). I checked the intake and exhaust pipes, they were clean. I cleaned the hose going to the pressure switch, I removed and bleach-cleaned the water container on the side of the furnace that holds the water from condensation. I removed, inspected the heather plate, no dirt, no cracks. I removed the turbulators from the secondary heat exchanger and cleaned them with soap and water (there was no deposits on them, just slight discoloration). I added high temp silicone when putting the heather plate back on, no difference in results after installation. To be safe on the safe side, I replaced both the pressure switch and the exhaust motor, no changes in behavior. Anyone have an idea of what else I can do? I have run out of ideas, there is a long wait until I can get a someone to come in.

I am working with a Ruud furnace in which it has a problem with the heating system and it is that when I put it in the heating mode it turns on the turbine, then it lights the spark and lights the flame but when it works for some 5 seconds or less it goes out everything and I get a code on the control board indicating code # 10 which tells me that it is from "1HOUR LOCKOUT" but I did the test on all the sensors and they are all in good working order and I wanted to know what else could be happening that case, thank you very much.