This is a gas fired furnace in a mobile home. I
have no idea how old it is.
Hopefully I can explain the problem.
The furnace runs well and gives off adequate heat.
The fan works good without any unusual noise.
Between the time the furnace shuts off and when it
starts again, the fan will cut in and run for
anywhere from 30 t0 45 seconds. The chamber does
not light. Just the fan goes for those few seconds.
Then sometime later the furnace will ignite the
chamber and the fan will cut in and the furnace
works normally. The fan cutting in does not happen
every time but say 80% of the time