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rutterback · Jul 28, 2009, 07:27 PM

I bought a Honeywell rth221b thermostat. I was smart enough NOT to mark the wires when I took off the old one.:mad: the wires that come out of the wall are red, green, white, and blue. The thermostat looks like this-

Y-o o-Rh
G-o o-Rc
o-W

Im assuming green to G, red to Rh (Rh and Rc have a jumper between) and white to W. Where in the world does blue go?? My heat worked but not my central air. Im assuming the A/C is the blue wire?

Like a typical guy, I threw away the instructions months ago and never checked to see if the AC worked... Smart... I know.

Thank you in advance for your help and tips.

KISS · Jul 28, 2009, 07:38 PM

Blue has to be (Outside unit - Y) especially if manual fan works because that is G. In AC mode the thermostat controls the fan.

ballengerb1 · Jul 28, 2009, 08:00 PM

You might want to print this out after reviewing it. https://www.askmehelpdesk.com/heatin...eat-58313.html I am thinking blue to yellow but read the whole thread.

dac122 · Jul 29, 2009, 06:03 AM

I also say blue wire to Y terminal. Here are your instructions.

rutterback · Jul 29, 2009, 02:32 PM

THANKS for the answers! Almost there!

This is what's on my furnace. How do I know if my AC unit has a transformer? I don't know if I should use the jumper.

Hope this is helpful!

siberianair · Jul 29, 2009, 02:35 PM

Need a jumper between rh and rc... blue goes to y terminal...

ballengerb1 · Jul 29, 2009, 02:36 PM

This looks bit odd to me. I see the blue wire going to the yellow terminatal but I also see another red going to the same terminal. I think it goes to the one vacant terminal marked G, what do you think KISS?

wmproop · Jul 29, 2009, 04:17 PM

Looks to me like the whitish-yellow and the red are the ones used to go outside to the ac unit,, this is OK rutterback

rutterback · Jul 29, 2009, 06:56 PM

Nothing is working... this is what my thermostat looks like... thanks again for everyone's patience.

rutterback · Jul 29, 2009, 07:13 PM

Which one should I try in the "G"?

Thank you

ballengerb1 · Jul 29, 2009, 07:20 PM

Move the red off the yellow leaving the blue still connected to yellow. Move red to the empty G on the right.

KISS · Jul 29, 2009, 09:34 PM

I think we need to start completely over. This looks way to simple and it should be working. Hah.

I propose - disconnect the thermostat.

We are going to "play thermostat". So before trying things disconnect power. Can I assume that you don't have a voltmeter? Leave the wires attached because they are disconnected at the other end. Just add the jumpers.

Jump R to Y and Gc at the furnace. Turn on furnace. Outside unit and fan should come on. Might have to wait 2-5 minutes. Fan will come on immediately.

Turn off power. Remove these jumpers.

Jump R to W. Turn on power. Furnace should comeon and a short time later, the furnace fan should come on.

Turn off furnace. Remove jumpers.

That checks out the furnace.

DO the tests and report back.

siberianair · Jul 30, 2009, 03:55 AM

Check the fuse near your circuit board or maybe you blew the transformer.
You did turn the power off before playing with wires on tstat didn't you?

rutterback · Aug 12, 2009, 12:58 PM

Nothing is working! Please help!! Its 95 outside!

rutterback · Aug 12, 2009, 01:04 PM

I never shut the power off like an idiot. I don't know if there is a voltmeter either? I'm going to try what KISS said... ill report back.. thank you

ballengerb1 · Aug 12, 2009, 01:40 PM

I never did understand siberairs comment and reddie to me. He said I was wrong but never explained further. I have not seen a board on the furnace with 2 wires going to it. The blue/yellow sends the signal, the second red should be jumpered at the stat.

ballengerb1 · Aug 13, 2009, 05:09 PM

This may amuse you but I see that Siberianair has been blocked out as a troll. Maybe skip his suggestions for now.

Smackcat73 · Jun 7, 2011, 04:03 AM

Rutterback--- what did you ever do to solve the problem? I'm having the same issue!