Ask Me Help Desk

Ask Me Help Desk (
-   Heating & Air Conditioning (
-   -   Thermostat color code? No Yellow Wire. (

  • Jul 9, 2007, 10:14 AM
    Thermostat color code? No Yellow Wire.
    Hi My Name Is Lindsay And Im Having Trouble Installing My New Honeywell thermostat:o it's a non digital thermostat, round one the old fashioned kind, I don't know where to connect which wire because I don't know which wire is which I have the following wires
    Wire Not Connected To Anything??
    Im Supposed to have a yellow wire I know that much but what color wire is the ac if I don't have yellow?
    Please Help Me Any Advise Is Better Than None... Have A Nioe Day Everyone:)

    Okay, More Info I Have A Heat Pump/Strip Whatever its called but its not gas but I can't figure out what color the ac wire is still?? Also Where Can I Find the colored wire connecting to the air handler? Also Where Do I Connect The Ground Wire?
  • Jul 9, 2007, 10:27 AM
    I have to disagree with the comment about any answer being better than none. I have seen plenty here that were much worse than nothing.

    This may be as simple as going to the furnace or air handler and making a list of what wire colors go to what terminals, red to R, white to W, etc. Then connect the same wires to the same terminals at the thermostat. Electricity is color blind. If you need more help, go to the sticky at the top of the forum and page down to the sections on wire colors and heat pumps. The orange and brown are a tip off you may have a heat pump. They require special thermostats and set ups.

    Red often connects to both RH and RC at the thermostat.
  • Jul 9, 2007, 03:56 PM
    First you have to determine which type system you have, heat pump or gas furnace. Once you have determined this you can then proceed to wire this correctly. I would rewire the control circuit to the standard norm,this will forestall any furture problems, post more information and I or someone else can give you instructions. Mike
  • Jul 12, 2007, 06:33 AM
    To get A/C from a heat pump, you need 3 things, the reversing valves must be in the right position, plus air handler relay coil and the compressor contactor coil must have power.

    Follow the cable from the thermostat to the air handler and see how the terminals there are marked. There should be a pair of wires going out to the outside compressor, often blue and yellow. Thermostats don't have a ground, but a common coming off the transformer and going directly to all the coils. Often it is a blue wire, and the terminal may be marked com. Usually the other other side of the transformer has a red wire going to the thermostat where power is switched to the right coils for each function.

    If the current wiring doesn't follow the conventional color codes, it might be best to straighten them out, but only after careful study of the sticky here, and making notes of where the wires are now.

    If the new thermostat doesn't have as many terminals as the old, it may not work. If they are different, you will need to carefully study the directions.
  • Jul 12, 2007, 12:39 PM
    Lindsay, now that we have determined that you have a heat pump we must first make sure you have a heat pump thermostat and the easiest way to tell for some one who is unfamiliar with the trade is to look at the terminels on the subbase of the thermostat, if you see terminels RC, RH, Y,W,G with no "O" or "B" terminels this thermostat will not work because it is not for heat pumps. Moving on, all the wires from the stat go to the air handler ( you may have to remove a panel to see them) also the wires from the outdoor unit will connect up here as well. Next remove the panel on the outside unit and look at what terminels are hooked to what wires, go back to air handler determine which wires (color) are hooked to air handler (there will be a common wire connection, same wire that you noted outside, "C") there will be a fan relay connection, normaly green wire from stat, and you might see additional wires depending on if you have aux. heat strips (check the wiring diagram on the panel door to determine) now go to thermostat and connect the same color wires to the thermostat that you noted outside and at the fan coil. The common colors will be red to R-C and R-H with a jumper, Y-1 to yellow, G to green, white to W-2, O to orange, B to blue (only one is used "O" or "B" not both depends on manufacturer) see which one was hooked up outside,W-2 and Y-2 wire colors may vary, determind by checking outside color wire for Y-2 connection and in air handler for W-2 connection to aux. to heat strips. Some thermostats have a "C" or common connection which will be the same color wire at the air handler and out door unit. And may I say good luck to you because your problem can stump the best. Mike
  • Jul 12, 2007, 12:43 PM
    I suggest you turn off all breakers before removing any panels. Mike
  • Jul 12, 2007, 07:12 PM
    Tell us what colors go to what letters on the old t-stat and what letters you have with the new stat and it will be a easy change out. Your older T-stat did not use a common wire and the new one may or may not need one. If your new T-stat takes a battery you may get by with the same wires you are using now with out getting inside the fan coil unit to do rewiring. Give us more info.
  • Nov 26, 2011, 03:17 AM
    Green Energizes Fan
    Brownish Heat Pump Reversing Valve
    White Energizes First Stage Heat
    Red Rc 24 Volt Hot for Cooling
    Red Rh 24 Volt Hot for Heating
    Orange Heat Pump Reversing Valve Energized In Cooling
    Blue Second Stage Cooling

  • All times are GMT -7. The time now is 12:17 PM.