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Nest not working with AC

CNYTeddy
Community Member

I installed my Nest successfully a month ago and have had no issues with my heat. However, when it came time to turn on the AC, it would activate the unit for a few seconds, then turn off. A few seconds later, would do the same. The AC would not stay on for more than a second or 2. 

I contacted my HVAC technician, and they said the problem was with the thermostat not communicating with the unit.

Any advice? I have a W, C, G, Y, and R wire. My old thermostat had the R wire going to RC, with a jumper from RC to RH. It also had the C and W wire both going into the W port.

8 REPLIES 8

TROBBS
Community Member

I have the same issue. I was online with Google Support today for two hours and never got any resolution, finally had to end the chat. I am a HVAC Tech and have done several installs and thermostat replacements, my unit is perfectly fine but when call for cooling starts the A/C starts up and immediately shuts down. I removed the Nest and installed old thermostat and it worked again. Its seems that the engineering team that designed the Nest did not want buyers to jumper any lines into the Nest Thermostat as such if you do, it sends the Nest into a "No power" failure mode and re-boots asking you to hold for 2mins 30secs as it starts back up. If I find a solution I will repost.🤔On restartOn restartBooting up sequenceBooting up sequence2:30sec delay2:30sec delay

TROBBS
Community Member

IMG_20220514_143205465.jpg

Went to the control board on unit and the common wire was not in common terminal, was in R terminal. Switched wire to C terminal and Nest is now cooling. 

 

Also CNYTeddy, pull the Common wire out of Nest terminal and tuck away from the other wires & mount Nest back on wall and try cooling mode without common. If it works without immediately shutting off, then it's a problem with where the Common wire is connected on your units control board. Hope this helps.

Fosswife
Community Member

How might we find out if the common wire is labeled wrong? We are having this same issue as stated above. But originally our Common wire (blue) was not connected. We thought connecting it might fix the problem but it troubleshoots us.

TROBBS
Community Member

You have to see where the Common wire (blue wire) connects to the terminal block on your HVAC unit. See the picture I posted; mine was not in the "C" terminal. After connecting it to the "C" terminal my Nest Thermostat worked properly and the A/C ran like it should.

CNYTeddy
Community Member

Nope, it was the thermostat. I swapped it out for a learning Nest (more expensive). Same problem. HVAC guy said they see alot of bad Nests. So I bought a cheaper Sensi, and what do you know- it worked right away, no issues. So it seems the problem was with the Nests.

Uhhh that’s crazy and frustrating. We got ours to work, but it runs until we manually change it to Eco or Off mode. I guess we will save money by limiting our ac use. 🤦‍♀️ Otherwise, maybe eventually replace the thermo again with something other than Nest. 

Brad
Community Specialist
Community Specialist

Hey there,

 

In an attempt to keep content in these forums fresh, we'll be locking and closing this thread. If you still need assistance with this issue, feel free to start a new thread. Thank you for your understanding.

 

Best regards,
Brad

TROBBS
Community Member

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