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Carrier Furnace w/ Honeywell WiFi Thermostat I have a Carrier furnace with the cheapest programmable thermostat (TB-PHP01) that came with my house. The thermostat uses six wires: Y, C, R, G, W, and O. Last year I purchased a Nest E but after hours on the phone with them I was still unable to get the cooling working. A couple of days back, I tried again this time with a Honeywell RTH6580WF WiFi thermostat and it's the same issue over and over again. The Honeywell backplate has the following connections:

K, Y2+L, W2 + AUX/E, G, W + 0/B, C, Y, R, Rc

Carrier thermostat backplate: Carrier thermostat backplate

I followed the instructions of Honeywell to the letter, as the instructions say "If your old thermostat had separate O and B wires, attach the B wire to the C terminal.":

Wire ---> backplate

Red ---> R

---> Rc bridged to R by metal jumper

Yellow ---> Y

Blue ---> C

Orange ---> W + O/B

Green ---> G

White ---> W2 + AUX/E

Honeywell backplate: Honeywell backplate

heat works, fan works but cooling (most important for me here in the Texan heat) does not work. According to what I can hear from my furnace it does not even gets commanded on when I select cool on the thermostat. I have followed the thermostat configuration and set the system to:

1 : 0 Heat/cool: Gas, oil or electric heating with central air conditioning

2 : - (this option never showed up)

3 : 1 Electric heat: Use this setting if you have an electric heating system (thermostat controls fan operation).

5 : 9 Electric furnace: Electric heating systems

I have always waited the 5 minute compressor protection wait time but to no avail: never switched to cooling ,"cool on" kept blinking. Does anyone have an idea?

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    Is this a heat pump system? That's normally where the orange/o/b wire comes into play. – JPhi1618 Jul 17 at 19:59
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    Can you post photos of the wiring at the air handler end of the system? – ThreePhaseEel Jul 17 at 23:09
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    ibb.co/7RTsz1n ibb.co/bQ4pqjC ibb.co/wJpp9sp ibb.co/wdD8xtL ibb.co/L1q4nnj ibb.co/8jqb6CN I did find a little box tucked in behind the furnace labeled "Aprilaire Ventilation Controller". I never noticed that device before and switched it off after some research. – ces Jul 18 at 13:00
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    Can you post a picture of the wiring diagram for your furnace, for that matter? – ThreePhaseEel Jul 19 at 2:30
  • Blinking means it's on delay; it makes you wait that 5min. If everything worked before, I'm going to assume the old one didn't even have a delay function, and that the zone control is the culprit, allowing the AC to be called and then immediately stopped to instead bring in fresh air. - I can't make heads or tails of the spaghetti porn pictures; all I can say is that the T-stat's O becomes a white wire after the zone control, because I don't even see an orange wire at the furnace... – Mazura Jul 19 at 20:36

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