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    tom1234's Avatar
    tom1234 Posts: 4, Reputation: 1
    New Member
    		  
    #1

    May 8, 2008, 01:49 PM
    4 Wire thermostat won't cool
    Our old thermostat display stopped working but the thermostat would still turn on it would just shut off right away. So I assumed it was just broken. I bought a new thermostat and now the fan and heat work but hot air comes out when it is on cool.

    The wires we have are:
    Green
    Yellow
    Blue
    Red

    On the old thermostat the Green went to G, the Red went to R, The Yellow went to Y and the Blue went to O.

    The new thermostat has holes for G,Y,W, Rc, Rh. And I connected Green to G, Yellow to Y, Blue to W. and the Red to the Rh with the jump included. I can't seem to figure out how to make this work. Attached at the bottom is the instructions for the new model. Thanks


    http://customer.honeywell.com/techli...0s/69-1799.pdf
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #2

    May 8, 2008, 04:36 PM
    Do you have a heat pump?
    tom1234's Avatar
    tom1234 Posts: 4, Reputation: 1
    New Member
    		  
    #3

    May 8, 2008, 06:25 PM
    To be honest I have no idea. I do not believe so. I live in my roomate's condo in Arizona and all of the equipment is on the roof.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #4

    May 8, 2008, 06:28 PM
    In many cases the O is for a reversing valve and those are in heat pumps. If that is the case you might have the wrong type thermostat.
    hvacservicetech_07's Avatar
    hvacservicetech_07 Posts: 1,083, Reputation: 75
    Ultra Member
    		  
    #5

    May 8, 2008, 08:30 PM
    I bet it's a heat pump. What is the brand of the old thermostat?
    tom1234's Avatar
    tom1234 Posts: 4, Reputation: 1
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    #6

    May 9, 2008, 03:51 PM
    The old thermostat was a honeywell. Model T8400C 1099. I figured thermostats were pretty standard so I didn't even check to see if it would work.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
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    #7

    May 9, 2008, 04:20 PM
    See here. Your old thermostat. Look under page two figure 6.

    http://customer.honeywell.com/techli...it/69-1484.pdf


    It says O can be used for single stage heat pump systems. I believe you will need a thermostat with the O in order to change over the reversing valve from heat to cool. You need a different thermostat.
    tom1234's Avatar
    tom1234 Posts: 4, Reputation: 1
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    #8

    May 10, 2008, 09:58 AM
    Purchased a new thermostat today(for a heat pump) and it appears to be working fine.

    Thanks for the help!
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #9

    May 10, 2008, 01:58 PM
    Glad it worked out for you.
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