Tony Hwang writes:
diyme wrote:
furnace exhaust fan turns on... then the heating element lights up....
then the gas ignites breafly and then gas shuts off..then the fan stays
on and it starts the process all over until it lights. most of the time
it lights on the second time.
It does not do this all the time but more then we like.
Why is this happening?? Can we fix this or do we need to call someone?
Goodman installed in late 1998.

Hi,
Two things to check; flame sensor and inducer pressure switch.
Sensor can have a fine surface rust causing intermittent operation,
switch can have a debris in the hose.

I just went through a perhaps similar problem. Ended up being a problem with
the condensate drain lines. Combination of blockage in the line
leading from the ventor motor exhaust port to the trap and a slight
slope in the distal end of the condensate tubing just before it
entered the condensate pump. These combined to cause the inducer
pressure switch to shut off after condensate started
accumulating.

However, if problem is that the flame first shuts off almost
immediately but then burns properly for a sustained period the second
time, it probably is not a condensate blockage problem. Since
condensate blockage should build up more the longer the flame burns.