lennox elite

tred

the furnace fires over and will run for about 2 mins then drops out. then comes back on and does the same thing. the board is flashing normal operation the whole time. the board never loses 24 between w and common. the flu pipes seem to be clear. the pressure switch was replaced last year and the flame sensor yesterday. the trap was also drained

Tony Pullen

check the high limit switch....also, if it is a 90% or better furnace, There has to be water in the trap to operate

screwdave

you might check the unit grounding, they are very sensative.
best bet is a differant brand

carmon

its possible its the stat.. remove r from board the n jump r -w see what happens then