My furnace will keep trying to
start, but will not fire for more then one second.
Many People Call a furnace a boiler
and a boiler a furnace. So the answer
you are looking for may be on the boiler
From a plumbers perspective this is the rule of thumb, If it
blows warm air through ducts, It is a
Furnace, If it has baseboard or
radiators it is a Boiler. If you need
help with your boiler or furnace please
Open Dialog Service.
Click On Any Image to see a Larger
This is what the Janitrol furnace
looks like with the cover closed. in
order for it to work with the air supply
and return, this unit was installed
upside down, this unit is designed to be
installed up right or upside down.
||Once the door id removed you can see
all of the parts that make up the
furnace, the control board, the blower
motor door switch, gas valve and other
parts, including the flame sensor, the
cause of this furnace's problem.
||Here are your combustion fan
your burner tubes, gas control valve,
hot surface igniter and most important
to this page the flame sensor.
||The orange wire in this picture
leads to the flame sensor, there is a
screw or a nut holding it in place,
remove the screw or nut to remove the
||This is the flame sensor, with the
orange wire connected, i inspected the
wire and found that it was in good
shape, it had no brakes in the
insulation, and did not need to be
||This is a close up of the flame
sensor, you may think that it is not
that dirty and could not be the cause of
the problem, sadly some inexperienced
plumbing and heating technicians, will
look at a flame sensor like this and
assume it is not the problem.
But they are very wrong, that little
misunderstanding has costs many
customers a small fortune in replacing
other parts that did not need to be
||A short explanation, on what this
does, Very simple it is a flame sensor,
so it feels the flame. But it only has 1
to 2 seconds to feel the heat from the
flame, and send the signal to the
control board. any delay and the board
shuts off the gas, and the furnace tries
again. So that little discoloring on the
flame sensor acts as insulation
preventing the flame sensor from feeling
the heat, in the very short time
allowed. In short, it needs to be
||I use a fine file to clean the flame
sensor, I found that grit cloth does not
get all of the carbon build up off of
the flame sensor. Note:
how it shines. this is good for another year. So simple if you know what
you are doing.
I hope you found this page usefull and
that you retund to this website the next
time you have a problem with your warm
Is this happening to you? There are a
number of reasons why a furnace will short cycle.
But I am only covering this one for now. This is a Janitrol Furnace. And it
is installed upside down. So it may look like yours but it is upside down.
On this unit, sometimes it would start and run for hours even days then it
would recycle over and over again, then it stopped all together.
I could see the igniter was working because I could see it glow. so I knew
it was not that. The next step for me is the flame censor.
This is the way it works thermostat calls for heat, combustion motor comes
on draft is good, power is sent to igniter, igniter gets hot, power is sent
to gas valve to open, gas valve opens for a few seconds waiting for a signal
from flame sensor. if it gets a signal the gas valve stays on till limit is
reached, if there is no signal from flame censer, the gas valve is turned
off. and the cycle starts again, and will do this a few times, after it
fails a number of times the circuit board locks out and the red light blinks
out a warning.
The problem is the
flame sensor (on this unit), (you can have the exact symptoms and it could be
another problem) And the solution is simple. take it out, clean it with a fine
file, get all the carbon off of it and put it back. the only time you have to
replace then is if the porcelain is cracked. the fourth picture from left shows
where it is mounted (remember this furnace is upside down) next how dirty it is,
then how to clean it. and how it should look. Good luck,
Monoxide Please read this
Modine Garage unit heaters