There is NO reason to get an answer as
you did on a forum like this!
This is a Q&A discussion board and
that's what you asked and here's
my personal experiences.

The numbers you quoted, "out of the box"
are probably fine. Usually
you can't adjust the upper limit .... is
that correct on your unit? On my
furnace, the limit switch and the fan
switch are 2 physical units. As for the
on/off temperature, you can adjust it up
or down. If you go down, you will
get more heat out of each furnace cycle,
however, at the risk of feeling a
cold draft from the now cooling down
heat exchanger. Even 90 degree
air moving can feel cold. My original
non adjustable switch in the furnace
was supposed to be something like
95/135, however, it, and a new replacement
unit from the factory, never even got
close to those numbers. I was more
like 120/155. I then put in an
adjustable unit and it works very well. I
adjusted it to allow the fan to run as
as low a temperature as possible and
still not feel too drafty. I think the
turn off temp is now something like 85
degrees. BTW, I asked a rep from the
furnace company about my experiences
and he said that he had done the same
thing on many units. I think the
manufacturer either had a bad batch of
fan switches or the placement on
the plenum was such that it didn't truly
represent the temp of the air flowing
out of the unit. The later was the
more probable. I hope this helps.

Jay Luke wrote:
Since I bought the house three years ago, the furnace has always operated as
follows:

- kicks in and blows heat for 30-45 seconds
- fan stops for 10-15 seconds
- repeats this cycle for 30 to 40 minutes, then the fan and the heating
stop
- 60 to 90 minutes later, starts all over

When I had my furnace vents professionaly cleaned the other day, I asked the
technician what his thoughts were, and he stated that this behaviour is due
to a faulty limit switch on the furnace. He quoted a price of $300 plus tax
to install a new one.

After researching online and verifying for myself that this was rapid
cycling, I went down to the local hardware store and found a new replacement
limiter switch for $40, so I purchased it. Installing should be
straightforward since the existing switch is exposed and already wired, so I
just need to set the start/stop limits on the switch.

How are the off/on temperature settings determined? The default settings on
the switch (out-of-box) a
Off: 95
On: 135
Limit 210

I can't refer to the current settings on the existing switch because the
tech had moved them around before leaving.

Anyone have any knowledge or advice on this?

Cheers in advance - jay