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I installed my Nest and now have a weird noise from the outside unit.

rgaila
Community Specialist
Community Specialist

Disclaimer: This thread was migrated from our previous version of the Google Nest Community. You can continue to receive updates on your thread issue here or simply ask, browse or more in the new Google Nest Community.

Original Poster: Steve Delray Beach  

I think I have the same problem described in this thread but its locked and I cant post in there asking for the permanent fix. 

 
 
I have not swapped my Y1 and G wires as I leave the fan on to move air in my house so I wasnt sure if that would make an impact on the fan. 
 
I noticed when it makes the noise from the outside unit, it feels like the air coming from the vents isnt cold any longer, it still blows air but feels like the ac isnt on. 
 
My AC guy said everything looks good and mentioned he wasnt a fan on the nest thermostats  and recommend I switch back to my old thermostat. That was a waste of $120 for him to come out. 
 
 
 
1 REPLY 1

rgaila
Community Specialist
Community Specialist

Hello Steve Delray Beach,

Apologies for the delay in response, and sorry to hear about your strange AC unit noises! I can understand the cause for alarm. Let's look into this issue together.

From the wiring setup screenshot you posted, it looks like you don't have a C-wire/Power Connector installed. From an old thread, the following explanation gives a great easy-to-understand approach to that noise.

"The Nest thermostat contains a rechargeable lithium ion battery. This battery runs the programming and keeps the thermostat connected to WiFi, but WiFi connectivity is draining – the battery doesn’t last very long on its own. So, to keep itself going, the Nest recharges itself from your HVAC system’s wiring.

In a system with a C-wire, the Nest charges itself from the C-wire’s current and all is fine.
In a system without a C-wire, though, Nest recharges its battery when the heating or cooling runs. It diverts a little bit of the power to itself and charges its own battery. This isn’t a new concept – illuminated doorbells and lighted switches use this same technique to take just enough power to light the little bulb inside without triggering the doorbell chime or opening your garage door.

In most systems this, too, works fine – assuming you’re running your heating or cooling frequently enough.
But let’s say you aren’t. Let’s say the weather’s mild and you’re just not running the heating or cooling that much right now.

In this case, Nest will very briefly attempt to draw power from your HVAC system on its own. Some users call this “power stealing”. The Nest only “power steals” when the HVAC system is off, and it stops when the system is on.

This call for power is meant to be brief and undetected, a tiny “pulse”, but some systems are very sensitive and see the Nest’s small power draw as a call to turn on. Of course, once the system is on then the Nest stops its attempt to charge itself and the furnace or AC turns off again, but then the Nest is still low battery so starts to draw power again. The end result is a furnace or A/C in a loop of rapidly turning on and off."

You may need to connect a C-wire or Power Connector for your device to charge consistently. Right now, it looks like you're receiving full power (anything above 3.6V is good) but it might be compromising your A/C.

Let us know how it goes! I hope we can resolve this issue together. If a C-wire doesn't fix your issue, we'll troubleshoot further or escalate to a case if necessary.

 

-From Garrett DS, Community Specialist.