I have a Lennox 80MGF3/4-100A-1 with a White-Rodgers 36E36-278 Gas Valve.
The furnace has been frequently going into WatchGuard mode since the burners fail to ignite. I cleaned the flame sensor and it functioned normally for a few weeks then started having the same issue. I would turn the furnace off/on repeatedly until it finally ignited.
During recent troubleshooting I was testing connections and moved the wire plugged into the C2 terminal on the gas valve. The burners immediately ignited and everything functioned normally for another week. The next time it failed to ignite, I simply moved the connector slightly and it worked for days again. I cleaned the contacts and confirmed a good connection.
It failed again today. I noticed that moving the connector slightly will either turn on or off the gas flow.
Is it the connection causing the issue or am I sending a signal when I move the wire into a dead spot that temporarily resets something and allows the furnace to run for awhile?
What are the chances that it's a loose connection in the terminal block itself?
I'm going to cut the wire back and attach a new spade connector to see if that is a fix but I'm looking for some advise on whether there is a known issue and I should be getting some parts on the way before I'm left stranded without heat.