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BillyHvac, Journeyman HVAC Tech
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I have an old thermostat and want to change it out for a new

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I have an old thermostat and want to change it out for a new honeywell wifi thermostat. The old one has an Rc and Rh jumper together with no C. What do I do?

Billy :

Hello my name is Billy


Hey Billy


What do I do with the Rc Rh wire?

How many wires do you have in the cable total and what colors are they?

How many wires do you have in the cable total and what colors are they?
Customer: replied 3 years ago.

there are 5






Thank you.

Was blue attached to anything?

I assume red was to rc/rh
white to w
yellow to y
green to g


Customer: replied 3 years ago.



Blue is attached to B

Thank you.

So you have a heat pump? Maybe a Rheem or Ruud?

Customer: replied 3 years ago.

I could not tell you.


can you give me the make and model of the outdoor ac unit? Or is this in a condo?

Customer: replied 3 years ago.

i went and looked at the heater - trane xe 80

ac is kenmore ca7 0600ka1

Thank you.

It is play on words (letters) when Trane is involved.

You may have a C wire and dont know it due to different terminology from different companies.

Do you mind removing the doors from the Trane furnace...find thermostat wire...and tell me if the Blue wire is on a B in the furnace?

Customer: replied 3 years ago.

the blue is not connected to anything along with the yellow

Ok we are close now.

What wire is attached to Y in thermostat and does that wire attach to terminal strip in furnace or direct to another wire?

Customer: replied 3 years ago.

The yellow is attached to the Y at the thermostat but is not attached to anything on the other end

This would mean the ac would not be working.

Rc/rh = 24v in from furnace
W = signal for heat out from thermostat
Y= signal for AC out from thermostat
G= signal for fan only out from thermostat.

In the furnace where R,W,G etc is you see a C, Com, or B terminal?

Customer: replied 3 years ago.

Yes the ac is not working


coming from outside unit will ne 2 thermostat wires. Do you see those and where they attach?

Customer: replied 3 years ago.

Yes that is correct. There is a green and white wire. No labels on the furnace to tell what the wires are attached to.

Thank you,

so at this point you have red, white and green hooked in furnace?

Customer: replied 3 years ago.


Do you have a terminal C, Com or B in the furnace?

Customer: replied 3 years ago.

I dont know what any of the wires are connected to. There is no labeling for them.


From left to right

Green - AC

white - F

Red - F

Green - F

White - AC

Can you take a pic of the wiring area in furnace and post here?

Or post at a file share site like

Customer: replied 3 years ago.

Thank you!!

The wire in pic to the right of the white wire on W....what letter is under that ?

Customer: replied 3 years ago.

wow. I cant believe I didnt see the letters. It is a Y

Is the wire on Y from the outdoor unit?

Almost the control a white rodgers 50a50?

Customer: replied 3 years ago.

Yes that would be coming from the outside a long with the white wire on the left.

Are you talking about the old thermostat?

Ok I think we got it....

The far left wire with the bluw ring connector.....and the far right wire on Y with blue ring connector go to outdoor unit...correct?

The red on R, green on g and white on W go to thermostat,,,right?

Then you want to take the yellow coiled on thermostat wire and attach to Y WITH the far right wire with ring connector.....Then take unused blue wire coiled on thermostat wire and attach with the far left wire with blue ring connector.

Follow so far?

Then in thermostat the blue goes to C

Customer: replied 3 years ago.

Yes two the first two statements. I follow what you are saying about all the wires. Now where do I connect the red wire on the thermostat?

Red wire goes to R.

You didnt mention what make/model thermostat...but it will be either R or a rc/rh with jumper.

If jumper in place it does not matter which you connect to, the rc or rh...

If any questions at all let me know.

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