I had to take a soft tooth brush to my orifices last summer after I had found my draft inducer full of water! The ac drain was plugged and filling the heater with water. Take a new dry brillo pad and clean that flame sensor. remove all them wires to the spark box and check for corrosion. Get a good ground to the burners or that box won't recognize flame and shut down.
If it still has intermittent pilot add a Re-ignitor to the pilot.
### SUCCESS WE HAVE IGNITION /LITE MAIN BURNERS! ###### SOLUTION #######
I went over there.. they made me some breakfast coffee.. raining like cats dogs outside... cold inside the whole house.. to my knowledge
this furnace has been sitting for years! without ever being fired up. But its would have fired anyways.
I took out the pilot line and pilot burner/igniter-sensor, didn't look too bad but was light brown burned color. The igniter-sensor probe
made out of tungsten or other hard metal was covered in it too. I took a fine emmery cloth to it and polished up the whole assembly
just as good as new. Even where the orange spark plug boot goes to. I cleaned up the part that it attaches to the burner assembly
and screwed it back on put the pilot line back on the Main valve assembly. I removed the Ignition Module just like JWWebster told me to
do and removed all wires and re-installed the box. NOTE: working with (millivolts) and not having a SOLID Ground will get you no where!
I know this by experience working on cars and their sensors not working right.
Everything set to go. RE-checked wires roll outs and sequencing. Pushed safety switch lockout and ignition! Pilot is lit.. Main Burners ON
system is stabilized main blower on after furnace plenum temp rise good to go! Temperature was stable with continuous burn in furnace.
Looks like we fixed it.
I would like to thank everyone who helped me on this project. Those schematics and manuals for valves, modules came in handy.
Customer is more than satisfied has a smile from ear to ear.. hands me an early Xmas present in my hand. (note: it was green too)
All I care is that the furnace is working and they are happy but the extra bonus was a plus for me.
My Background is Radio communications/electronics, Hold Extra Class License. Electrician by trade when I was younger, Computer Technology
major with MS Certifications Current job functions IT/Windows servers. I have plenty of skills to fall back on but computers is my favorite. I
enjoy countless hours working with my hands and its something I have a passion for. HVAC was a trade my father told me to get into when I
was younger but never finished the classes. I kick myself in the head for not following through with that. But nonetheless, I can still get
these monsters up and running.. and not without your help.
Thanks again.. you are all so knowledgeable