Atwood Furnace

[sg4082]

I have a 2002 American Eagle that has 2 Coleman Mach 8 A/C's, a Coleman thermostat model # AR7854 and two Atwood RV furnaces. The problem I am having is the zone 2 furnace will not come on. Two weeks ago I was in Oklahoma City and used both furnaces overnight, the zone 1 furnace ran all night and the zone 2 furnace shut off in the middle of the night throwing a single flash/pause code on the circuit board (air flow/limit fault). When I got home I checked and of course there were dirt dobber nests in the exhaust tubes. Cleaned them out, purchased screens and tried to start again. Same thing, zone 1 works fine nothing on two. Changed the zone 1 plug to the zone 2 furnace to make sure it wasn't the unit. Zone 2 came on fine and ran continually. Moved the plugs back to there correct units, same results, 1 flash and three second pause on circuit board. I had a spare thermostat in the unit when I bought it 6 months ago, so I switched the thermostat thinking it may be bad. Same results, zone 1 yes, zone 2 no. Pulled the fuse on the thermostat as the tech rep suggested, waited 5 minutes, put the fuse back in waited 5 minutes tried to start, same results. I should say that I have traced the 12v power all the way down the system up to the circuit board and I have power to the board. I need to know if anyone knows how to "reset" the thermostat power to clear the board. Thanks for any help in advance.