[anjp]

I have an Armstrong high efficiency gas furnace model g1d91bu075d12b. The furnace will not ignite and the LED indicator shows 3 flashes "pressure switch open with inducer on"

Here's what happens:
1- house is cold. Thermostat is set higher than house temp
2-furnace kicks on... well, inducer fan kicks on for about 10 seconds
3-furnace heat box glows
4-nothing fires. No ignition
5-inducer fan turns off.
6-led displays 3 red flashes

My understanding with hvac is beginner. I understand that this means the inducer (blower motor?) is working, but the pressure switch is off. Here are a couple photos of my unit with top panel off:





I believe the pressure switch is the black disk in the top right of the main shot.

Here's what I tried:
1 - power off power on
2 - unplugging & reconnecting the grey and black hoses on the pressure switch side
3 - unplugging the grey hose on the inducer side and sucking in (I hear a click from the switch)
4 - unplugging one of the wires from the siwtch, power off, power on.
5 - reconnecting the wire
6 - power off, power on

... no change. Can anyone help? My wife is getting cold!