wrote in message
ups.com...
OK, so I am an idiot. Sorry about this. The way that I see it (not
knowing anything about this stuff) is that it sounds like the heat
"kicks on" and then turns off after 20-30 seconds. This continues to
happen until the desired temperature is reached. I don't know if it is
the blower or the burners, I can just hear it loudly come on and then
turn off. This is a natural gas furnace that I hav elittle information
on, as we just moved in. There is nothing blocking any of the vents,
and the room does eventually get to the desired temperature. If I have
to bring someone in, I will. I just wanted to make sure it wasn't
something that I can do very easily. Thanks again for any help someone
can give me.


Do you have a Lennox Pulse furnace? if so..first, allow me to offer my most
sincere condolences.

If its a Pulse, its just acting normal.

If you can get to the furnace, you need to see if its the burners. But I
doubt it. Sounds like you might have (remember, no one can see it from here,
but offer educated guesses) is a fan limit switch thats either set WAY to
low, or, if its a newer unit, a bad limit switch.

The cycle should be, and this is assuming its an induction style unit, with
a draft inducer motor.

1-Call for heat by thermostat
2-self check of board, and initial start of inducer motor and fan
3-after board check, all safety switches involved with inducer close,
ignition souce will start (hot surface will be engergized, or spark ignition
will start)
4-pilot valve in gas valve will open, once flame is proven to board, gas
valve will go to 100% flow
5-fan limit switch will either start to register temp rise in unit, and
start blower at or around 150F air temp, OR, after a timed delay by board,
fan will start.


IF you have an older fan limit switch that is adjustable, it may be set too
low. This will also cause cycle issues with the fan in the summer.
I would not adjust it over 100F on shutdown, but then your problem might be
that its out of calibration anyway. it can also be caused by a fire rate
thats not set correctly.

It also, but rarely can be caused by a motor that for whatever reason, is
tripping out on a thermal limit, indicating normally a blower motor, or
capacitor that is bad. IF its the blower cycling out due to this, and its a
capacitor, and its been doing this for some time, go on and replace the
motor as well.