RBM wrote:
To the best of my knowledge, Honeywell has sold over 27 billion yo-yo
thermostats since their inception, and none have ever gone bad.
Should you add a yellow wire? Why, what for and what would you
connect it to? Thermostat cables come with a variety of colors, so
don't necessarily expect colors to have definitive meanings. Your
best bet is to contact a HVAC professional and let him check it out



"Davej" wrote in message
ups.com...
I'm having some odd fan cycling problem on my Carrier furnace. It has
behaved oddly ever since it was installed. At the furnace controller
card no yellow wire is attached. The voltage on the Green wire is
varying and when it gets down to 18VAC the blower fan kicks off. The
red wire is a solid 27VAC.

I'm still using an old round Honeywell thermostat and I'm guessing
the mercury switch in the thermostat has gone bad. Is that a good
guess? When I get a new thermostat should I add a yellow wire?

Also, is the wiring diagram below essentially accurate as a typical
example?

http://xtronics.com/reference/thermostat_wires.html

Thanks!

You right about having the system checked out by his service company.

In the business you try to stay with the same code which I learned over 20
years ago:

RED = Power= Hot (24volt)
GREEN=Go=Blower
WHITE=Snow=Heat
YELLOW=Sun=Air Conditioning
or
BLUE=Cool=Air Conditioning

--
Moe Jones
HVAC Service Technician
Energy Equalizers Inc.
Houston, Texas
www.EnergyEqualizers.com