I have a puzzling problem. When I select "Cool" on my thermostat, the
central fan does not come on, and so, while the air conditioner
outside runs, it quickly freezes, as there is no air movement. On the
other hand, if I select the heat-cool switch to "Off" and turn the fan
"On" the fan works fine. But if while the fan is running, I move the
Heat-Cool switch to "Cool" the fan shuts off. I have replace the
thermostat, and have the same problem.
Any help will be greatly appreciated, as the outdoor temperature is
Is your thermostat such that you can access the wires connected to it
while it is operational? you ought to slap a meter on there and figure
out if the issue is with the thermostat not commanding the fan to be on
or if it's in the furnace. If your furnace is like mine, the fan is
controlled at different speeds for each of heat, cool, and manual fan on
- so at least in my case, if I were having your problem I'd be digging
into the control board for the furnace not the thermostat. If however
you have a single speed fan, it would likely be the thermostat. Which
kind of setup do you have?
replace "roosters" with "cox" to reply.
Model of outside unit, furnace inside and your thermostat?
Do you have a multimeter? How many wires are on the 'stat.
When you are calling for cooling, you should see 24V AC between
terminals on the 'stat R and G and again between R and Y(since outside
fan runs you must see 24V AC here) If you don't see 24V AC between R and
G 'stat is bad.
It sounds like a wiring problem somewhere. You already confirmed the
fan and compressor are working, which is good. You just need to
confirm if the wiring is correct. If it is, it could be a defective
circuit board on your A/C unit.
If ( R ) on the indoor unit is connected to ( G ) on the thermostat
and ( G ) on the indoor unit is connected to ( R ) thermostat then
with the fan on it would connect G to R and with the cooling on R
to ( Y ) with ( G ) OFF
Check the wire colour on the indoor Unit R - Y - W - G and make
sure these are connected to the right thermostat terminals
All of the wiring seems to be correct in accordance with the
installation instructions. And still, when I turn the "Heat-Cool"
switch "Off" and move the fan switch from "Auto" to "On" the fan comes
on. If I put the fan switch on "Auto" and turn the AC to "Cool" the
AC fan comes on and cold air enters the building, but wothout the fan,
it does not move and the AC unit soon freezes up.
1- Check the Wire link R to Ro is inserted
2- Check fan setting switch set to F
3-Put the wire going to G on the thermostat to the R
Terminal on the thermostat so the R terminal has
two wires R and G ( The fan should run without )
changing the thermostat switch )
Cycling the system
Make up a jumper wire one foot long - bare a 1/4 inch at
1 Bridge R to G Fan should run
2 Bridge R to Y cooling should start after timer delay
3 Bridge R to W Heating
24 V is a low voltage however care should be taken
R is the 24V Active which is switched by the Stat to
Outputs G + Y ( Cooling ) G + W ( Heating ) G Fan
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