I have a 6 month old Lennox G51mp furnace and last night the furnace started working intermittently and the temp dropped to 60 degrees by this am. Called the service provider and he came by and said that the filter was dirty and had caused the problem. Looked and it was dirty but not that dirty...
Later on the furnace started acting up again, turning on for short periods then off, never getting up to more then 68 degrees. Called again, wife spoke to him as I was at work and he said that because the filter had been dirty the control board had to be replaced because the 'high limit' was open and the furnace was overworked causing the control board to blow? Meanwhile, after his first visit the furnace ran fine for a while then the intermittent running again with both filters out.
Is this plausible? I've looked at the Lennox online doc for the furnace and it doesn't mention causes of the control board failing.