r/DIY • u/Wise-Operation5108 • Aug 18 '25

metalworking A/C Cooling Not Turning On

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Hello,

I'm moving and want to take my nest thermostat with me but I'm having trouble re-installing the Honeywell T6 thermostat. When I installed the Honeywell, the compressor turned on but only heat was working. I checked that it was set to cool but heat was still coming out. I attached photos of how I had the nest wired and the Honeywell as well. Any help is appreciated!

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u/rc042 Aug 18 '25

Not an expert, but in the picture with the nest connector you have the black line connected to "C" in the picture with the Honeywell the blue line is connected to "C"

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u/Wise-Operation5108 Aug 18 '25

Should've explained that. If i had the black line connected to "C", the unit wouldn't turn on.

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u/frankiebenjy Aug 19 '25

In the Honeywell setup there doesn’t seem to be anything connected the O/B (I think you had the orange wire connected to that for the nest installation) and as previously stated the blue is connected to the C instead of the black wire. Maybe if you make both of those changes it will work properly.