My honeywell rth2300 has W,G,R,and B, COLORED wires connected, and my old thermostat had a yellow and white cable attached to mercury. To my understanding, digital thermostats don't have mercury, but they will lack connection of wires because there are only 4 coming out of the wall. How do I make the connections on the back of the thermostat so it can stop, when the right temp. hits 77 degrees.

I assume this is a heat only application and not a millivolt system?

The RTH stat must be battery powered and you can use the terminals R and W.

Well, that was a given, the batteries were on. But the question you didn't read it properly, which was How do I make my a/c unit stop when it hits the temperature that I set it at? Meaning the outside unit and the inside unit keep running without stopping when it hits, say! 78 degrees.

OK, sorry misunderstood.

Manual is here: http://customer.honeywell.com/techli.../69-2327ES.pdf

The stat has G Y W R and O/B

A "B" wire may mean a heat pump or it could be 24 VAC common.

So, do you have a heat pump? The default configuration of the thermostat will be wrong for a "B" terminal and a heat pump.
It will be cooling in the heating position and vice versa.

Generally the 4 wire connection was for a gas furnace and no common wire.
R = 24 vac
G = Fan
Y = outdoor compressor
W = heat

If conventional, then the furnace controls the fan in heat mode. In cool mode, the thermostat controls the fan.

Need to know if you have a heat pump, the old connections (if known) and if the unit is a TRANE.

Don't know about heat, I live in Florida and I've never turned the heat. The unit is a rheem.

This is going to be hard.

What color wires do you have coming out of the wall?

If we assume red(R), yellow(Y), green(G) and white(?), then...

Turn off the unit (breakers)
Connect red and green together
Turn on the unit (breakers)
- the inside fan should come on.

Turn off the unit
Connect red an yellow together.
Turn on the unit
-The outside unit should come on

If those tests work, then
Turn off the unit
Connect R, W and Y together
Turn on unit for about 10 minutes.

Observe whether you get hot or cold air.

Are you saying you do not have a yellow wire?? If not then
Red to R jumped to Rc
Blue to y
White to w
Green to G

Also did you do the correct installer setup?

Well I only have B, R, G, W no yellow

B could be brown, blue or could be black. It's also a terminal Letter for a heat pump system.

Four wires could be a conventional system or a heat pump system assuming both heat and cool and in Florida.

Simple question.

What wire colors do you have?

What terminals did you have on your old thermostat?

Do you know what color wire WAS connected to WHAT terminal?

Otherwise we have to figure it out in one of a few ways:
1. Match terminals from old/new
2. trial and error
3. Look at how they are connected at the furnace.

And do whatever is easiest.

Are you able to take pictures?

See how simple it can be? https://www.askmehelpdesk.com/heatin...at-468307.html

Well I just connected the wires back again as you explained on the last segment, with the exception of the Y left out blank.
Connection is as follows:
B=blue coming out of the wall
y= blank, no wire out of wall
R= red coming out of the wall
G= green coming out of the wall
W=white coming out of the wall

then I connected a bridge between
R to G and B

R= POWER
G= INSIDE UNIT
B= OUTSIDE UNIT

It's now working but I have to see if it shuts itself automatically
I have the COOL and AUTO switches on

I believe you will have to connect the blue wire to the Y terminal of the thermostat.

Do you have a gas line connected to the furnace?

The "B" terminal will not shut off automatically. I'm going to suggest that you connect the blue wire to the "Y" terminal.

Well, I don't see what I typed on my iPhone to keepitsimple, but thanks for everything I solved the matter by calling my a/c technician and the problem was solved.
So you are known for future questions by anyone else, although it will be very rare for it to happen, the solution was very simple. All the colored cables go to the corresponding letters on the thermostat with the exception of the blue wire which goes to the Y on the thermostat. Then the Temperature has to be risen to about 90 degrees for the a/c to kick in and start the auto turning on and off like the old one. That is all to do! Thanks for all the advice keepitsimple, you were very helpful and corteous! beto2win.

Thanks.