Thermostat Green Wire Not Connected -Let’s Fix it!

Each wire of your thermostat is tasked with its own specific job. If one wire malfunctions or fails to connect, the entire process gets disrupted.

In this article, I will talk all about the green wire. And why you are facing issues like the thermostat green wire not connected.

In most cases, it happens due to a power issue. If the wire end of your G wire is not straight or not properly corroded, the wire connection issue can happen. Also not inserting the wire end fully into the wire connector can lead to the g wire not getting connected.

That was just a preview. You need more details in this matter to get your issue fixed. Keep reading the article to know more.

Wyze Thermostat G Wire Not Connected 

G wire not connecting

G wire not connecting is one of the common issues of Wyze thermostats. Here we will see how to deal with it.


Though there have been many complaints about the wyze g wire not being connected issue, no substantial reason has been pointed out. Though some say it happens due to a power issue. Or the wire end needs to be secured or it is corroded.

There are many theories about solving this issue. Here I’ve handpicked two possible ways you can solve the wyze thermostat g wire issue.

Solution 1: Bypass G Wire

One way you can fix this and finish your setup is by bypassing the G wire.

  • While going through your setup, you will get messages like “missing g wire”
  • You can tell the app that you do not have a green (G) wire by clicking the “no g wire” option. Doing so will let you pass the setup.

However, it is better to note that, you won’t have the full functionality of the system or the unit.

Because the green wire typically controls the blower fan. So, if you bypass the g wire, the heat and the fan will not come on. But the AC should work fine.

So, basically, you can bypass the app by applying this technique where the app won’t detect the G Wire. However, you won’t get the heat.

Solution 2: G Goes into C 

This is another way to fix the g wire issue.

  • First of all, start by disconnecting the C wire from the unit as well as Tstat. 
  • Now proceed through the app setup. You will get a suggestion to use the C wire adapter. But that is in case you select R, Y, W, and G with no C. You need to follow the given directions for your C wire adapter.
  • On tstat, you’ll be notified to connect R, W, Y, and C (G will go into C). Do accordingly and finish your setup. 

Google Nest Thermostat Green wire Undetected/ Not Connected: Reasons and Solution

Installing a Google nest thermostat in your home is always a great choice. As you have the option to add a second nest thermostat, as well. However, it also has the same g-wire issue.

There can be several reasons behind the message showing the thermostat G wire is not connected to google nest. Here I have included the possible ones. Along with that, I have provided ways to fix it in a step-by-step process. 


If your google nest thermostat is not detecting the G wire, it may show messages that make it look like the wire is not connected. Even though it is.

One reason why it happens can be due to a power issue. Maybe the wire end is not straight or it has not been fully inserted into the wire connector. It can also happen if the wire end is corroded. This can also cause issues like the nest thermostat not cooling properly.

Thermostats usually detect any wire by testing it in two ways. 

One is testing it mechanically, that is whether that wire is inserted into the connector. Another way is: electrically which refers to the electrical current in the wire. 

So, in case a certain wire fails either of these tests, then you may receive messages like “wires aren’t connected/detected”. 

Solution: Strip and Fix the Wire

To fix the unconnected or undetected G wire you just have to follow the simple ‘Strip and Fix wire’ technique. Go through the following steps. 

Step 1: Start off by turning the system’s power off at the fuse box. It will protect the system as well as the thermostat from possible damage.

Step 2: Then remove your thermostat display from its base. 

Step 3: Now pull out the G wire and thoroughly inspect it. The exposed part of this wire needs to be approximately ⅓ to ½ inches long. It also should be straight and clean.

Step 4: If you find any crooked or corroded ends of that wire, you need to cut and re-strip it.

Strip and Fix the Wire

With the help of a wire striper you can do it effortlessly. Follow this video.

However, keep in mind that if the wire end is corroded or short, you won’t be able to strip or cut the wire any further. In that case, your only option would be to clean the corroded wire using a corrosion cleaner

Step 5: Once you are done, re-insert that wire. Another thing you need to ensure is that your wire connector’s button needs to stay down. 

Otherwise, your wire is not fully inserted. As a result, your thermostat won’t be able to detect the wire. 

Step 6: If you want to be more cautious, you can repeat the same steps with all the other wires also. 

After you are done checking, push the display back over the base til it makes a click sound.

Step 7: Complete the process by turning the power to your system on again. 

And this time, the G wire issue should be fixed.

Why is G Wire Needed on the Thermostat?

G wire mainly controls the blower fan. The job of this blower fan is to push the air through all the vents in a house. 

The thermostat generally regulates the fan in cooling mode. So, in case you do not have the G wire attached to the thermostat, that fan will never come on.

As you can see, G wire is not really needed for heating mode. You need it for cooling. 

Well, in rare occurrences, you can wire up a relay into the air handler. It can allow the fan to operate for cooling. So, you can do without the G wire.

However, in the most frequent and normal scenarios, it is the thermostat that makes the connection. Then the fan comes on its cooling mode hence G is required.

Identifying Thermostat Wires Using Thermostat Wire Color Coding

Thermostat Wire Color Coding

Here I have provided a quick summary of all the wires of different colors. Have a look.

White Wire:

The job of this white wire on a thermostat is to connect to the heating system. It unites your thermostat to the furnace.

Yellow Wire:

The yellow thermostat wire you see beside the white one usually connects to the compressor. It turns the compressor on and off and thus controls the air conditioning system

The Green Wire:

Your thermostat’s green wire typically connects to the blower fan of the furnace or air handler. It is in total control of the blower fan.

Green Wire

The Orange Wire:

The orange wire regulates the heat pump. The wire works as a connector between the thermostat and the outdoor condenser. It helps reverse valve functions from hot to cold.

Red Wires:

Red wires tend to connect to the main power source. This Rc/Rh wire supplies power to the thermostat.

The Rc Wire:

The Rc wire is for air conditioning systems. It can also work for dual transformer systems.

The Rh Wire:

And Rh wire will connect to the heating system of the thermostat. 

The Blue (C) Wire:

Blue wires are also known as ‘C’ wires as they are the common wires. These wires are essential for all the smart thermostat out there that needs a 24/7 power supply. 

As you can see, thermostat wire color coding can be a bit confusing. So, having a general idea about each of those should save you some extra hassle.

Frequently Asked Questions (FAQs): 

Can I use G wire as C wire?

Yes, in case there is no C wire in your thermostat, you can use a G wire. But keep in mind that, by doing so you won’t be able to use the fan independently. Because the heating and cooling won’t be running. Also, note that most HVAC systems tend to be incompatible with this method.

What does E wire do in the thermostat?

The E wire on your thermostat turns the emergency heat on and off. Emergency heat is generally used when the weather gets too cold outside. In such cases, the regular heater can’t keep your house warm and resorts to applying emergency heat.

How does the thermostat get power?

A thermostat can be supplied power through batteries. Or you can run a line from your furnace.  Thermostats are typically powered using the 24V from the transformer. The transformer is found inside the HVAC equipment.

Wrapping Up 

Hope you have got the basic idea about the issue of the thermostat green wire not connected.

Use the steps in this article to fix it. Also, to avoid such situations with G wire or any of the other wires, inspect your wire regularly. Follow the proper maintenance guidelines to keep your thermostat in good shape.

This is all for today. Have an incredible day ahead!

Leave a Comment