I found your forum after having some issues with my furnace. Age is unknown because I rent and my landlords are out of town.

When I went to turn the furnace on tonight, nothing happened. House temp registering 68-69 at thermostat, furnace doesn't kick on when adjusted to 72.

Fan will turn on when set to "fan" on.

A/C side works fine.

Cycled through the steps listed here (and on the inside cover of the furnace).
*Set temp on thermostat to lowest
*Cut power
*Turn gas switch off, wait 5 minutes
*turn gas switch on
*Turn power back on
*Set thermostat to desired temp

At this point, the thermostat will click and "heat on" will come on.

Down at the furnace, nothing is happening but the blinking LED.

Code says "23" which is pressure switch obstructed or off.

Turned unit off and checked the pressure switch according to the directions found here (gently sucking and blowing through the hose) and no obstructions were felt.

Cycled back through the instructions and got the same result. The blower won't kick on at all unless the fan is set to on.

Any and all help is appreciated.