[rd16917]

I was going to replace my Aprilaire 8334 thermostat (Bryant gas furnace) with a Honeywell programmable, but after removing the Aprilaire found that builder cut a hole in the wall bigger than the new thermostat. So I reinstalled the Aprilaire, and all seems to work except the heat won't shut off after reaching set temp. (Differential is set to 1 degree.) Plus there's a lot of clicking going on when I turn heat on.

I noticed when I was removing the old thermostat that the blue wire was attached to W terminal. But I didn't note where the white wire was attached. (I know, I'm kicking myself for not labeling the wires before I removed the old thermostat - duh - lesson learned.)

So I wired everything according to color code:
Red - RH (jumper to RC)
White - W
Yellow - Y
Blue - B
Green - G

Does the blue wire go to the W terminal? If so, where does the white wire go?

Thanks for the help.

[labman]

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. Many have RH and RC to allow separate transformers for heating and cooling. With just one red wire, jumper them. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.

Go to the furnace and see where the blue and white are connected. It will work with a blue wire running from one W terminal to the other, but you may as well follow the convention.

[NorthernHeat]

Tell me where the wires go at the furnace. The Blue terminal is for a heat pump reversing valve and wouldn't be used unless you have a heat pump.