# Furnace or Thermostat problem?



## bootpdx (Dec 6, 2009)

I have a 2 year old Bryant 90 gas furnace and the thing works like a champ in heat mode. Problem is, when I switch it over to fan either auto or on modes, nothing happens. I have a raging wood stove fire and want to circulate the heat, but can't because I have no fan mode. Are there different blowers? One for heat and one for fan? Could it be a relay?

Any input is greatly appreciated, thanks


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## travelover (Dec 6, 2009)

There is just one blower motor. Possibly the thermostat?


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## bootpdx (Dec 7, 2009)

travelover said:


> There is just one blower motor. Possibly the thermostat?



Thanks, I think your on to something. Looking at the Thermostat, there is only one white wire coming in and it's connected to the W terminal on the Therm. There is no fan wire, not quite sure where that leaves me, do I have to run a additional wire from the furnace to the Therm?


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## kok328 (Dec 7, 2009)

Take a closer look, there has to be a minimum of two wires in the thermostat to establish heat.
A red wire attached to the R terminal and a white wire attached to the W terminal.
The thermostat completes the 24VAC circuit between the two to energize the controls to induce heat mode on your furnace.
To use the fan "ON" option on your thermostat you'll need a green wire attached to the G terminal (on both the thermostat and the furnace).
Take a close look at the brown insulated wire running between the furnace and the thermostat.  Sometimes the installer will cut those back if not in use.  In which case you'll have to see if you can pull some slack further up to the thermostat and strip back some insulation to expose the additional wires (red, white, green, yellow, etc..).


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## bootpdx (Dec 7, 2009)

Kok328-
right on. You're right. there is a white and a red both within white insulation, which I peeled back, but didn't see any additional wire. Looks like I'll have to run a new one, but I'm heading down to check out the furnace end of things first. This is a new therm, because the old dial type is on a different wall with it's wires cut. Not sure why p/o wouldn't have set it up to run a fan. weird.


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