Thermostat shows wrong temp after adding c wire?

[MG24]

I recently changed from a traditional thermostat to a Nest. It was working fine, but said it needed a C Wire so I added one. This is the one I got from Amazon: 

24 Volt Transformer, C Wire Adapter Thermostats, Compatible with Ecobee, Nest and Honeywell Smart WiFi Thermostat, Ring Nest Hello Skybell August Doorbell (White) https://a.co/d/dIgcSX1

now the temperature is off by 8 or so degrees (too hot). I’m worried something is overheating? It doesn’t feel hot but it’s definitely not 70 degrees in my house.

During install there were two wires for the c wire, so one went into c, and the other is now sharing a slot with another wire. Is this the problem? What do I do? I don’t want to burn out my nest but I need heat. The two wires on the c wire look indistinguishable.

thank you!

[MG24]

 this is the current wire configuration 

[CoolingWizard]

The way that you have this item you purchase from Amazon connected is not electrically valid for the thermostat. The problem you have is to separate power source is going to the R wire. it is imperative that R wire power being received from the HVAC equipment is the same power source that is going back to the equipment on the return wires such as Y, W, and G. If you look at the wiring example showing you on the Amazon ad, it shows you to wire the two wires to a separate R and the C. Specifically, the thermostat was taking power in from the HVAC equipment on the RC terminal. And the separate transformer was wired to the Rh terminal and the C or common terminal. In order to achieve this, you would need a Nest learning thermostat second generation or third generation.

In your picture, it looks like you have an unused blue wire conductor. You should use that blue wire to connect to the C terminal on the nest thermostat, and then go to your HVAC unit, find the blue wire, and connected to the common terminal, or the common side of the HVAC transformer.

Ken, the AC Cooling Wizard

[MG24]

Thank you so much for taking the time to explain. Can you clarify this for me?

“find the blue wire, and connected to the common terminal, or the common side of the HVAC transformer.”

the HVAC is connected by a wire in the wall… I haven’t even done anything there so far and have no experience. Should I hire someone?

lastly will keeping it as currently configured ruin the nest? Thank you 

[CoolingWizard]

Did I see the wire properly there. Is there a blue wire that’s not being used as sort of wrapped around the brown cable sheath? 
often HVAC technicians will take the unused wires behind the thermostat and wrap them around the outer sheath to keep them back out of the way. At the other end of the cable will be the HVAC air handler unit or a package unit if it’s all in one system, say on your roof or on the side of your house. The same wires that are not used while you used to be wrapped around that brown outer sheets. Know what I’m saying you would need to do is go to the other end where your air handler is, and I speak as if you have a split system, part outside and part inside the house. The indoor unit/furnace/air handler/system is where your thermostat cable goes . If you go to this unit, you will see the thermostat brown outer cable. She’s going in to the air handler unit on one side or the other or possibly the top. That will be the cabinet door. You will need to take off to find the other end. The first thing you must do, there is find the power disconnect, and turn off the power to the air handler unit.
you will either need a 5/16 inch driver or a quarter inch driver to remove the screw that hold the cover panel on.  Once removed you can locate the end of the thermostat cable. Find the same spare wire conductor color. in your case, they say, it’s the blue one, if the cable has the blue wire, wrapped around it, just unwrap it. How did that cover? You will find one of two things. An integrated furnace control board or a standalone transformer and various wires connected to the thermostat wires using wire nuts.  An integrated furnace control board will have screw terminals on it with letters like R, Y, G, and C,. You will need to attach the blue conductor to the C screw terminal. 
Now, if your furnace does not have an integrated furnace control board. You’re going to have to do a little more effort to locate the common wire of the transformer.

leaving that transformer connected the way it is will generate an electrical feedback which will generate excessive energy in the form of heat. Too much heat will indeed damage your thermostat.

Ken, the AC Cooling Wizard

[Markjosephp]

Hello folks,

I wanted to ensure that everything was covered here.

On point! That's very informative, Ken. Thanks for the help.

@MG24, I hope you've got the answer you're looking for. You can also try resetting your thermostat to default to update the wiring configuration. If you're still in need of assistance, feel free to let us know.

Regards,

Mark

[Markjosephp]

Hi MG24,

I wanted to follow up and see if you are still in need of any help. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further.

Thanks,

Mark

[MG24]

Thanks so much for following up. This is all really great advice but it’s so above my head. I need someone in Los Angeles who can set it up for me… do you happen to have a referral? Ontrac is who Nest recommends on their site but they apparently don’t do nest installs anymore and their phone number redirects to dish network. Thank you 

[CoolingWizard]

MG24, 

I do not know of anyone personally in your area. I am 4.5 hours south of you. That transformer you added how far does those two white wires run? Can you pull a new thermostat cable between your thermostat location and the HVAC air handler?

Ken, The AC Cooling Wizard

[Markjosephp]

Hi there,

Thanks for the continued support, Ken.

@MG24, I appreciate your effort. Before reaching out to an HVAC technician for the installation, we need to know more about your systems' configuration with Ken's questions above to better look into it for you.

Regards,

Mark

[Markjosephp]

Hello MG24,

I'm checking back in — how's it going? Still need our help?

Regards,
Mark

[Markjosephp]

Hi MG24,

It has been a few days since your last reply, and we're going to lock the thread within 24 hours. If you have any questions, please feel free to create a new post.

Thanks,

Mark