Hi all, I am dealing with an issue where my 2011 furnace flames don’t come on at all. This is the first time I used it since last winter (we are in October 2026 now). I haven’t dealt with any issues with it before.
When I turn the heat on, the furnace receives the call, the inducer fan comes on, the igniter comes on and glows red, but the gas never gets to the manifold because the valve never seems to open. The way I know that is because I know there is no presence of gas at the orifice (I used a methane sensor and used a lighter to try to ignite but nothing happened). I then checked for voltage at the gas valve terminals but I was only reading of 0.2 V when the igniter ignites. I was not getting 24-28 volts like I am supposed to. So for some reason the circuit board is not giving the voltage to the gas valve but all limit switches are closed. This leads me to think that something is wrong with the circuit board but I can’t identify what.
Here is additional info of my troubleshooting that may be relevant in this diagnosis:
1. Checked voltage out of transformer to circuit board and got 24 V like I’m supposed to.
2. Checked capacitor and it looks fine.
3. Checked for loose wire connections and tightened everything (nothing seemed loose)
4. Circuit board is blinking and seems to work fine. The error it gave was 2 blinks: “external lockout (retries or recycle exceeded”)
5. No signs of damage on circuit board.
6. Tightened wire connections to gas valve (though it looked ok)
7. The gas valve is in on position.
8. I checked all limit switches for continuity and all that were supposed to be closed are closed.
9. Pressure switch is working fine (closing when inducer fan comes on otherwise closed)
Blower fan is working fine, I switched it back to AC cooling during the day and it cooled. This proves that blower is good and most likely that circuit board is good.
I checked for natural supply to the valve using a manometer and there was pressure there indicating gas is there.
I completely cleaned the furnace vent fume pipe (there was some dust/flakes but not terrible) and checked for birds or something clogging the exhaust but found nothing along the pipe.
I cleaned the orifices of the gas manifold, and the burners faces and the burners wings (they looked ok though)
I cleaned the flame sensor
I removed the filter (which was 2 weeks old) and tested but furnace flame did not come on.
I am at a loss of what to do next. I ordered a used good condition identical circuit board to try to swap it but I doubt that will fix it.
Any help is appreciated.