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    apd1212's Avatar
    apd1212 Posts: 3, Reputation: 1
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    #1

    May 30, 2010, 02:29 PM
    Replace honeywell t87f with honeywell rth7500d for A/C and Heat
    I'm trying to replace my Honeywell T87F thermostat with a Honeywell RTH7500D. Have tried all combos and can't seem to get it to work. Here's the 4-wire connections to the T87F:
    Blue Wire --> Y terminal
    White Wire --> W terminal
    Red Wire --> R terminal
    Green Wire --> G terminal

    Thanks in advance
    Joshdta's Avatar
    Joshdta Posts: 2,549, Reputation: 45
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    #2

    May 30, 2010, 03:32 PM

    Why will it not work? Did you do a installer setup? Does your new stat require 24 volts to run? Or will it run off battries?? Did you put a jumper from rh to rc??
    apd1212's Avatar
    apd1212 Posts: 3, Reputation: 1
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    #3

    May 30, 2010, 03:51 PM

    The symptoms are
    For A/C - fan comes on but condenser does not
    For heat - heater fires up but fan does not come on
    I do have the rh to rc jumper

    The new stat can run on batteries and I didn't see anything in the instructions about an installer set up

    Thanks
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #4

    May 30, 2010, 03:54 PM

    Select Fan only, what happens?
    apd1212's Avatar
    apd1212 Posts: 3, Reputation: 1
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    #5

    May 30, 2010, 05:54 PM

    Fan only works fine
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #6

    May 30, 2010, 06:01 PM

    Switch Blue and White wires
    Joshdta's Avatar
    Joshdta Posts: 2,549, Reputation: 45
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    #7

    May 30, 2010, 06:53 PM
    Quote Originally Posted by KeepItSimpleStupid View Post
    Switch Blue and White wires
    If the white and the blue were backward the heat would not come on in the heating cycle would it??

    This is turning out to be a very odd problem for such a easy job
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #8

    May 30, 2010, 07:04 PM

    True. Have to put thinking cap on.
    Joshdta's Avatar
    Joshdta Posts: 2,549, Reputation: 45
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    #9

    May 30, 2010, 07:16 PM

    I am going back to installer setup problem. Sense he did not do one it may be running on heatpump, or electric furnace. You do have the b on y? Not y1 or y2? What is throwing me off is why the fan will not come on in heat mode
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #10

    May 30, 2010, 08:35 PM

    Could no AC, be because the breaker/fuse is tripped for the AC. Can happen if the Heat breaker was not turned off when changing the stat?
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