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    Sadney's Avatar
    Sadney Posts: 1, Reputation: 1
    New Member
    		  
    #1

    Jan 22, 2008, 02:52 PM
    Replacing old Honeywell A/C thermostat
    I am replacing my old Honeywell thermostat but am not sure of the correct part number of the old unit. The following numbers are printed on the old unit - T8085D1008 or 890121The replacement is a Honeywell, part# RTH7400D1008 Programmable Thermostat and I'm badly in need of some guidance regarding the wiring. My A/C system is an apartment combination heating and cooling unit.

    Thanks!!
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #2

    Jan 22, 2008, 03:15 PM
    Old thermostat wiring.

    http://customer.honeywell.com/techli...0s/69-0258.pdf

    New thermostat wiring

    http://customer.honeywell.com/techli...0s/69-1726.pdf

    It is all here for you from these two docs.
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