I have an old 20+ years automatic ignition Rheem Furnace Mod RGNC-14KC.
After a lot of thought and research these is where I am.
1) I turned the gas off and I can see the sparks from the ignition --> therefore thermostat OK, igniter OK, DSI seems OK.
2) I was able to light the pilot with a long match after making sure all gas had dissipated. I just turned the switch on with the match in and the pilot started. Pilot stayed on, furnace kicked in, home getting warm --> flame sensor OK, Thermocouple OK, pilot orifice OK (main reason I did this was to check if gas was flowing or pilot might be blocked).
3) when I let the furnace start on its own without the match it will not. I can hear a clicking sound as if the ignition is sparking but pilot does not come on. I looked inside while this is going on and best I can tell there is no real spark just a soft spark sound. In fact when the pilot came on with the match it seem to be blowing gas quite hard. Is it possible there is too much gas blowing on the DSI preventing it from sparking or is it that there is something wrong with the ignition system?
I would appreciate any help.