"Jay Luke" wrote in message
news:7wISe.224715$HI.196868@edtnps84...
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

I recommend that you get a manual for the unit and see what the manufacture
says. Or hire a licensed pro to do the job. I am in a quandry as to why you
would wait 3 years to fix this problem.