New Thermostat, now furnace blows cool air

Is there a switch that turns the blower(fan) on. It sounds like it may be in the "on" position. It would also help if you describe the system, thermostat terminals ,number of wires and their colors

The thermostat I bought is a Honeywell RTH230B. It is a 4 wire system. The color of the wires are red,yellow,black,blue. There is switch on the thermostat for fan but that is in the auto position. When that switch is on the AC fan turns on. Stupid me did not mark the wires when they were on the old thermostat.

RBM (remove this) wrote:

This sentence is wrong. Should read "I hear the blower turn on when I switch from off to heat."

snipped-for-privacy@gmail.com wrote:

Very tough without having noted the wire positions on the old stat. The "usual" wire colors would be R-W-G-Y. Let's assume Red is the RC-RH wire, there should be a jumper across those two terminals on the stat. Connect red to them. Next, touch each of the three remaining wires to that red wire, until you find the one that turns the blower on. Connect the blower wire to the "G" terminal. Next touch each of the remaining two wires to the red wire until you find which one turns on the furnace, connect that wire to the "W" terminal, and the last wire to the "Y" terminal.

What type heat do you have. Standard wiring would be.

red power 24v white heat yellow cooling green fan

You need to find out what blue and black function as for your system. The wiring placement for the previous stat would help.

It may be useful to check the connections on the furnace itself. If the connectors are labelled on the furnace you could match that against the thermostat connections.

Might save some trial and error.

Chris

Checking the wires against the red wire worked. Thanks for the info. After looking at the wire colors again thery were Red,Blue, Green (not black), and yellow. Thanks again for this quick and easy fix.

Have a great holiday

RBM (remove this) wrote:

Hi, Very good idea!

Some have a switch on the back for "furnace controls fan" or "thermostat controls fan". You may have this set wrong.