I have a Lennox HE propane furnace in the cottage that is set to 41 degrees when we are not there. We head up most weekends and when we get their I boost the temp to 65 deg and get a fire going in the wood stove.
The problem is the furnace will run for 40 to 45 minutes then shut down, although the thermostat may only indicate 45 degrees. The code points to burners failed to ignite. I reset the trip and again we'll run another 30-40 minutes and shut down. So it's takes for ever for the cottage to heat up. I have cleaned the ac condenser, replaced filter, cleaned flame sensor and igniter but problem still exists. Any ideas before I call a service guy which is over an hour away?