[Kathleenb]

I replaced a White-Rodgers thermostat with a Simple Comfort 2000. The old thermostat had the yellow wire attached to the unit. No yellow wire is coming out of the wall. The new unit does not have a yellow wire attached but does have a terminal for it. Can I run it without the yellow wire or should I do something to make up for the fact that it is missing from the wall? Thank you for your help with this.

[wmproop]

check the furnace end,, the Tstat wires hook up to control board and are labeled as to what they are,, G=fan,, W=heat,, R=hot,wire with 24 volts that send power to the TStat,, and yellow =a/c,, this is the usual rule of thumb,, so,hook the tstat wire into tstat the same way,, if you don`t have central air,, you don`t need the yellow

[labman]

The yellow wire usually runs to the coil of the A/C compressor outside. Do you have central air?

[Kathleenb]

Thank you for helping with this, yes, I do have central air and I connected the thermostat as follows Green wire to G, White wire to W, Red wire to Rc with a jump to Rh and then connected the blue wire to Y. Initially, it didn't come on but I called a friend and he said wait because of a delay. It is working great and I didn't short anything out (which is great because my husband was already upset by my initial tampering). Thanks again for your help.

[labman]

Check the sticky at https://www.askmehelpdesk.com/heatin...ons-58313.html
I think it mentions sometimes it is a blue wire that runs from the Y terminal out to the A/C unit. You may be good to go. Just make sure the blue wire doesn't connect to com at the furnace.