Originally Posted by rbs
Atwood AFM series furnace 2015 Classic will not light, diagnostic light indicates "flame sense fault". Furnace ran fine last week when we used it, but now just blows cold air. Have plenty of propane, wondered if anyone might have a suggestion for what
to look for?
When your furnace ignites, the actual igniter probe sends a millivolt signal back to the igniter control board to keep the LP solenoid (normally closed) open so that the LP supply continues to flow and the flame continues to burn until the thermostat is satisfied.
That sequence, and your 'flame sense fault' indicates that you have an issue either with the igniter probe, the igniter board itself or the connection between both.
Try cleaning the igniter probe with alcohol and a Scotch Brite pad and remove and replace the connector a few times to remove any residual corrosion. If you still have the fault, replace your igniter board with the appropriate model from Dinosaur Electronics, which make aerospace quality boards in the USA.