Armstrong Air Ultra V Tech 91 Furnace No Heat/No Flame

Problem:
Furnace seems to be working, but the fan simply blows out cold air.  There's no heat coming out whatsoever.  Can't even turn off heat using the thermostat. 

Solution:
Find out that the filter is dirty and that the burner is inflaming.  Replace the filter, and reset.

The furnace has two panels that can be taken off by lifting straight up to expose the inside.  You should see the handles with the word "lift."  Take off the top panel.  You should see several parts inside.  If you follow the gas pipe in, you should see the gas control which has a switch "on" and "off."  Next to the on/off switch, you should see a light.  That light is a diagnostic indicator.  On the backside of the panel that you take off, you should see the diagram and the information for the diagnostic light.  In my case, it flashes 4 times "Limit or Rollout Switch Open."  Above the gas control, you should see a rectangular box with a little circular plastic, look-through opening.  This is where you should see the flame.  In my case, I don't even see a flame. 

I need to reset.  To do this, you have to turn off the power to the furnace.  You should find a switch next to the furnace.  It should be very obvious.  It's just like a normal light switch.  Switching it off will turn off the furnace.  You should notice that the furnace is not running anymore.  After that, switch the gas control (described earlier) to off also. 

With those done, if you look beyond the gas control through to the back, you should see a brown rectangular circuit board with two wires running to it, with an arrow running in between.  The board is held up with two screws, one on top and one on the bottom.  Use a screwdriver, unscrew those and slowly pull out the board.  On the back of that board, you should see a big wire connecting the two connectors and a little black button with a silver cap.  Tap that silver cap a couple of times.  Put that board back where it was.  Turn the gas control to "on."  Turn the the power switch on.  If you look through the tiny circular opening, you should see the flame.  If you do, congratulations.  The furnace works again.

Disclaimer:  This solves my problem.  If it doesn't work for you, I'm sorry, but it may be something else.  If you don't feel comfortable troubleshooting yourself, call a professional.  When you work with electricity, fire and gas, it is dangerous, so be VERY, VERY CAREFUL.