enter image description hereThjis is where tech disconnected cables from thermostat (red and white) and connected directly to this Becket EniSysenter image description hereenter image description hereenter image description hereenter image description hereenter image description hereenter image description hereI am trying to connect a Nest E thermorstat on my HVAC unit that runs heat and AC. i have yellow-y1, G-green,White-w, red- R. When y1 is connected i get the error No power to R, i see the C wire on the cable, i connected the blue to C and make sure is connected to C on the furnace and AC but i get no power. I have to disconnect C and Y1 for heat to turn on but no AC. temperature in Connecticut now is 60F its not to cold to get those errors. Should i just buy a 24 AC wall transformer and connect it to the R and C cables to the thermostat? Nest tech support tells me C wire is not grounded, but i see it grounded on the board.

  • Can you include a wiring diagram for your HVAC unit? And/or a picture of the control board? What were the wires connected to on your old thermostat? – mmathis Apr 25 '18 at 15:07
  • Hi,. The connection to the old thermostat were the following. y to yellow, g to green, w to white, red to rc. I can get you a picture of the diagram and HVAC control unit as soon I get home. – Allan Apr 25 '18 at 18:39
  • Also take and post a picture of the actual connections at the furnace end of the thermostat cable. – Tyson Apr 25 '18 at 20:29
  • sorry guys, i got the pictures, but where do i upload them? cant see a button for uploading – Allan Apr 25 '18 at 22:27
  • @Allan -- it's the button that looks like a framed picture, next to the two braces button – ThreePhaseEel Apr 25 '18 at 22:51

You will need a wire going from the C on the thermostat to the C on the furnace, 5 wires total. R to R, W to W, Y to Y, G to G and C to C. At the furnace there will also be a second wire on the Y and C and they will go to your condensing unit. I can not tell from your pictures but it looks like the blue wire on the furnace C is probably going to the condensing unit.

  • There are two blue wires connected to the board. One from thermostat and one to condense unit. – Allan Apr 26 '18 at 0:37
  • I don’t see any blue wire at either one of the thermostats. I see green, red, yellow and white. Your old thermostat looks like it was battery powered since there is no C terminal. – user76730 Apr 26 '18 at 0:41
  • When I connect the blue wire in the thermostat I get a power issue on the nest e. I was told by nest tech support to disconnect it because it's not grounded. We had to take off the yellow and blue to make it work, but only heat is working. – Allan Apr 26 '18 at 0:45
  • Now I just noticed the white cable and red cable are not connected to the R and W on the board. I am posting a new picture – Allan Apr 26 '18 at 0:47
  • Now I remember... I had my furnace maintenance two months ago, the tech saw a problem with the relay so he disconnected the red and white and connected them directly, maybe that's causing the problem? I am posting a picture now.. – Allan Apr 26 '18 at 0:52

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