Common wire - Nest thermostat- help

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Old 11-04-19, 01:32 PM
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Common wire - Nest thermostat- help

Hello,
I’m having problems with my nest thermostat, attached are the pics for the cables coming from the furnace and ac and to the wall mount. Seems the thermostat is not getting power.
I noticed that the c wire(blue) coming from the furnace is attached to the red cable coming from the AC, the blue wire from the wall plate is attached to the the red cable coming from the AC, shouldn’t the C(blue) common wire be connected to the blue C wire going to the wall plate?
 
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Last edited by PJmax; 11-04-19 at 04:59 PM. Reason: removed dead links
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Old 11-04-19, 05:04 PM
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I removed your non working links. They were probably at a site that DIY does not allow.
I can hardly see you pictures but the Y wire coming from the thermostat should go to one of the condenser wires and the other condenser wire goes to C. Your description is not clear.
 
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Old 11-04-19, 07:18 PM
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Hi, thank you, can you suggest a better site to upload pics to? I tried attaching them but only got uploaded at 12kb as opposed to 500kb size. There is no y wire.
The furnace has 4 cables coming out, C(blue), W(White), G(green) and R(red)
The ac has a red and white cable
The wall plate has 4 cables, R,G,C & W.

From furnace C is attached to AC red
From furnace G is attached to wall Green
From furnace W is attached to wall White
From furnace R is attached to wall Red

From AC White is attached to Wall Blue
 

Last edited by Foxtrot_01; 11-04-19 at 07:27 PM. Reason: Trying to add pics
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Old 11-04-19, 08:35 PM
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The board will take pics up to 2-3 mb. It will only display 600x600.
It's easiest to load pictures here from a laptop. I wouldn't even consider using a phone.

You are really confusing the issue.
A splice in the middle of no where is bad from the start.

You have four wires to the thermostat.....
Green to G
Red to R
White to W
Blue to Y.
You don't have a spare for C.
You may have to run the nest without the C wire.
 
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Old 11-05-19, 09:55 AM
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Hello, I agree about the mid cable break, this is not my property Iím renting and I asked my landlord permission to look into the cabling, I bought a Lux bridge because Iíve been having problems feeding power to the nest thermostat, the battery keeps draining and I have to take it off the plate and charge it via usb. Upon further inspection I saw that there is a common wire coming out of the furnace but itís connected to the AC instead.

I tried uploading the pics but it might be that Iím using an iPad. So if you can suggest a host that works with the forum I would appreciate it.

From the furnace there is a C wire but instead of being connected to the blue wire(thermostat) itís being connected to the red wire from the AC, the white wire from the AC is connected to the thermostat blue(C) wire.
The rest green furnace to green thermostat, white furnace to white thermostat and red furnace to red thermostat are fine.
 
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Old 11-05-19, 02:04 PM
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Yes, the ac White is going to the thermostat Y with a blue wire but why is the blue wire from C in the furnace is connected to the red wire from the AC?
Why is the common wire from the furnace feeding power to the AC (red wire)?
 
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Old 11-05-19, 10:11 PM
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Remember..... you are dealing with AC so there is no polarity. Your A/C condenser needs 24vAC to operate. It gets its 24v common on the red wire and the 24v hot on the white wire. Makes no difference if they are switched.

You need five wires to the thermostat to have a C connection there.

If you wanted to lose the separate blower control at the thermostat.....
there is way to convert the green wire to C.
 
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Old 11-07-19, 12:48 PM
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don't waste your time with the nest especially without a common.
 
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