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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I'm having issues with wiring my new honeywell thermostat.

Customer Question

I'm having issues with wiring my new honeywell thermostat. The old one I'm trying to replace was Honeywell rectangular in shape, it has switches at the bottom for: cool-heat, on/off/auto etc. Inside was a dial that ticked & what seems to be a mercury based system. I've taken a picture before removing the wiring which includes the following:
R- Red Wire
O- White Wire
C- Brown Wire
G- Blue Wire
Y connecting W - Yellow conncted on the "W"side
New Thermostat "Honeywell 6450/6350 I cant seem to get the AC to blow out cold air. I read brown wire is a common and doesn't get used but when I check what I believe is the fernace and the brown wire is connected with all the other wires. But I havent connected it to anything as there is no "C" slot on my new Honeywell. Some assistance would be greatly appreciated. Thank you in advance.
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.


Please use the paper clip icon at the right end of the tool bar to send me that picture of the original thermostat connections..

Next look for a honeywell thermostat model number that starts with THW and give me that number or the model number off of the box.

So far it sounds like the original installer did not follow the generally accepted color code, and that is what is causing the confusion.

I also need to know if the unit that sits outside is a heat pump or not, a heat pump runs that unit in winter as well as the summer, and will say 'heat pump' on its name plate.

I will be in for another half hour tonight, if I miss your response tonite I will pick it up in the morning.

We can go from there.

Expert:  Phil replied 1 year ago.

I can also use a photo of the printed circuit board in the blower compartment of the furnace or air handler where the thermostat wires all connect.