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Often, individuals encounter alerts like ‘Heating is delayed' or ‘Cooling is delayed' on their Nest thermostat, and this can be perplexing. Persistent appearances of these messages could potentially signal a problem with the power supply of the thermostat.

There are two ways that Nest Thermostats receive power:

  1. The HVAC equipment (such as the furnace) powers and recharges the internal battery when it is turned on.
  2. Additional charging occurs through the common wire or C-Wire.

In certain scenarios, your thermostat simply does not get enough power from your HVAC equipment when it is turned on, resulting in a low-power state.

This low-power state is the cause of the delayed message you receive along with a number of other problems and malfunctions that can occur within your HVAC controls.

Read on to find out how to temporarily fix this problem, along with 5 ways to supply your thermostat with a C-Wire.

TLDR – Links to Devices to supply power

A C-Wire alternative designed for Nest Thermostat
A generic C-Wire alternative
24 volt transformer for a nearby power outlet

Differences in battery types based on the Nest Thermostat model

Newer models, such as the Nest Thermostat E and Nest Learning Thermostat later generations feature an internal rechargeable battery that users cannot replace independently.

The furnace powers and recharges the internal battery when turned on, while further charging occurs through a common wire.

Whereas the older Nest Thermostat operates on two 1.5V AAA alkaline batteries, which require replacement as they deplete.

Nest Thermostat Delayed
No C-Wire In Place

Nest Thermostat Delayed: Low power going to your thermostat.

Low power going to your thermostat can cause various issues, including delays in your Nest thermostat's operation. Unlike traditional thermostats, Nest devices require more power to support their advanced functions, such as Wi-Fi connectivity, motion sensors, and other smart features.

When the integrated rechargeable battery drains too quickly, the thermostat may struggle to regulate heating, cooling, and fan operation consistently.

Can function without a C-wire

Although Nest thermostats can technically function without a C-wire, sometimes they cannot draw enough power from the heating or cooling system alone.

This lack of power may cause problems, such as the “Nest Thermostat Delayed” message.

To resolve this issue and restore proper functioning, you'll need to inspect the C-wire connection on your Nest thermostat.

Simply detach the display and examine the panel labeled ‘C', where a blue wire should be present if you're experiencing low power issues.

If you don’t see one, installing a C-wire provides a consistent power source, helping to prevent future delays and malfunctions in your smart thermostat system.

Purpose of the C-Wire and the internal battery

The C-wire, also known as the “common” wire, is crucial for providing a continuous power supply to your Nest thermostat.

Unlike the Rh and Rc wires, which only provide power when switched on, the C-wire allows for a steady flow of electricity to the thermostat at all times.

This constant power source helps in maintaining the thermostat's internal battery.

A healthy battery ensures that all smart features of your Nest thermostat operate smoothly, such as Wi-Fi connectivity, software updates, and motion sensing.

Impact of Continuous Power 

Having a continuous power source through the C-wire prevents your Nest thermostat from experiencing low voltage issues.

As mentioned, certain actions and features require a specific voltage, and when the battery voltage drops, these features may not function properly or at all.

In extremely low voltage cases, the Nest thermostat may even disable its screen to preserve the remaining battery life.

By connecting the C-wire to your thermostat, you can maintain a consistent power supply, ensuring all of the smart functions and features work efficiently, and avoiding any potential delays or malfunctions.

Nest Thermostat

Temporary Solution: Charge the Thermostat

A temporary solution to the “Delayed” error message on your Nest Thermostat is charging the device.

  • To do this, carefully take the thermostat display off the wall
  • Connect the appropriate micro-USB charging cable to both the thermostat and a power source, such as a USB wall charger or your laptop's USB port. The charging process may take anywhere from 30 minutes to 2 hours.
  • Keep an eye out for a flashing red light on the thermostat, which indicates that it is charging.
  • Once fully charged, reattach the display to the wall.

While this charging method can resolve the “Delayed” error temporarily, it is not a long-term solution.

Check out the below solutions to permanently fix this issue.

Permanent Solution: Provide a C-Wire to your Nest Thermostat

To permanently resolve Nest thermostat delays, consider adding a C-Wire to your system. Firstly check if one is installed, by going to “Settings” and “Equipment” on the thermostat.

If one isn’t installed then check out the options below. If there is one installed, check out our other solutions section below.

Option 1: Hardwire a C-Wire

To hardwire a C-wire, you'll need to connect it to both your HVAC system and your Nest thermostat.

Make sure you turn off the power to your equipment before installation to ensure safety.

Keep in mind that this process can be a significant task if there is no spare wire available, as the wiring between your furnace and thermostat likely runs behind walls or in hard-to-reach locations.

Below are the steps involved for scenarios where there is an unused wire not connected to either the thermostat or the HVAC system.

  1. Turn off the power supply to your HVAC system and verify that it is off.
  2. Remove the face plate of your Nest thermostat and take a picture of the wiring for reference. Label each wire with the corresponding terminal letter.
  3. Check if you have an unused wire that can be used as a C-Wire. If not, you may need to run a new wire from your system to your thermostat. (Or check out the other options below). The C-Wire is typically blue. Connect the wire to the C terminal on the Nest.
  4. Find the other end of the thermostat wiring near your HVAC equipment, and identify the unused wire. Connect it to the C / Com terminal on the control board of your system.
  5. Finally, restore power to the furnace and Nest, reattach the Nest display cover, and test to see if your thermostat is working properly. You can confirm the blue C wire now appears as connected under “Equipment.”
Nest Thermostat Blinking Lights

Option 2: Use the Nest Power Connector

A C-Wire alternative designed for Nest Thermostat

The Nest Power Connector comes in handy for providing a stable power source to your Nest thermostat if your heating, ventilation, and air conditioning (HVAC) system is unable to deliver consistent power.

  • A comprehensive alternative to connecting a common wire (C wire) or hiring a professional installer to run a new C wire, the Nest Power Connector is compatible with the Nest Thermostat, Nest Learning Thermostat (3rd gen), and Nest Thermostat E.

To install, simply plug it into the wall and connect the black and white wires to your system's power terminals, while attaching the red wire to the C terminal.

The connector then transmits a signal to the thermostat, alerting it when to turn the system on or off.

Fixes Power Issues

A Nest Power Connector or C wire can help fix power-related issues, such as a rapidly draining battery or Wi-Fi disconnections, by providing a stable power supply to your Nest thermostat.

If you're not comfortable doing it yourself, a professional installer can manage the process for you.

Option 3: Use a Common Maker

A Common Maker, such as the Fast-STAT, offers a convenient solution for connecting a C-Wire without pulling additional cables.

It features a wireless sender and receiver that simplify the process, making it a time-saving and cost-effective alternative to rewiring your thermostat.

A generic C-Wire alternative

The Fast-STAT Common Maker consists of two components: a sender, which is connected to the thermostat, and a receiver, which is installed at your furnace.

  • By adding a common "C" connection to your thermostat, it allows a 24-Volt power source to be included in the existing installation.
  • Additionally, the Fast-STAT can accommodate a distance of up to 300 feet between the sender and receiver when using an 18 AWG cable, and it doesn't require any batteries.

Option 4: Install a C-Wire Adapter

Installing a C-Wire adapter is an effective DIY solution if your Nest thermostat setup lacks the necessary C-wire and you don’t want the hassle of installing the Nest Power Connector or Common Maker.

These adapters, designed specifically for the Nest thermostat, are user-friendly and easy to install.

By plugging the adapter into a nearby outlet and wiring it directly to your thermostat, you can eliminate the Delayed message.

To minimize visible wires, simply run the adapter wire along the wall or within it.

24 volt transformer for a nearby power outlet

This versatile adapter powers popular smart thermostats and doorbells while ensuring safe device charging.

  • With an 8-meter (315-inch) long cable, you can conveniently plug the adapter into an outlet without worrying about distance limitations.

Option 5: Reuse your G Wire as a C Wire

The G-wire is the green wire that enables independent control of your blower fan and is not to be confused with a ground wire. In this solution, you’ll be removing it from the G-terminal in the thermostat and installing it the same way for a C-wire. 

The same needs to be completed at the furnace. Using this is a cheap and easy way to get continuous power to your thermostat however you do lose independent control over your ventilation fan.

  • Verify your HVAC system compatibility: Before starting, ensure that your HVAC system will not be affected by the repurposing of the G-wire.
  • Loss of independent fan control: Be aware that using the G-wire as a C-wire means you'll no longer have the option to use the fan on its own or in “fan-only” mode.
  • Disconnect the G-wire: Carefully remove the G-wire from the G terminal in the thermostat.
  • Connect G-wire to the C terminal: Attach the G-wire to the C-terminal within the thermostat, setting it up like a C-wire.
  • Repeat at the furnace: Perform the same process at the furnace to ensure proper functioning.
  • Consider zone panel compatibility: If your HVAC system has a zone panel, this option may not be feasible, so check compatibility beforehand.
  • Jumper cable connection: Depending on your system, you might need to connect a jumper cable between the empty G-terminal and Y-terminal for proper functionality.

Other Causes & Solutions

Advanced Software Features Draining Battery

Advanced software features can potentially drain your Nest thermostat's battery faster than the C-Wire or equipment can recharge it.

To prevent this issue, verify that your thermostat's software is up-to-date and consider disabling certain features to save battery life.

Nest Thermostat 1

In recent months, Nest thermostats have received software updates to enhance sensor accuracy and Wi-Fi connection reliability.

Additionally, set your smartphone to automatically update the Nest app and Google Home app, ensuring you always have the latest features and improvements.

Loose C-Wire Connection

A loose C-wire connection can cause Nest thermostat delays, as the necessary power supply to the battery may be inconsistent.

To resolve this issue, inspect your wiring to identify any loose connections and secure them firmly, ensuring uninterrupted power to your Nest thermostat and improved performance.

Faulty HVAC Power Source

A faulty HVAC power source can cause your Nest thermostat to experience delays, even if it's properly connected to a C-wire.

To troubleshoot this issue, check your HVAC equipment for any visible damage or loose connections, and ensure the power supply is functioning correctly.

If necessary, consult a professional technician to assess and repair the problem, as this will not only fix the Nest thermostat delays but also contribute to the overall efficiency of your HVAC system.

Battery Failing

A failing internal battery is a common cause of Nest thermostat delays. Integrated batteries should last 5 – 10 years however some may have defects resulting in a shorter life span.

If your battery is on its last legs and is under warranty, you may be able to get a free replacement.

Nest thermostat batteries are non-serviceable parts so it’s not possible to replace them.

Get Professional Help with a Nest Pro

If you're uncertain about the issue or aren’t confident in resolving it yourself, consider contacting a local Nest Pro for help.

These professionals possess the knowledge and skills to identify and rectify any problems with your thermostat and HVAC system.

They'll also handle more complex tasks, such as connecting a C wire or a Nest Power Connector if required.

A Nest Pro offers specialized installation services for Nest devices, such as thermostats, through Google's partners Handy and OnTech.

These services offer the convenience of online scheduling, availability during evenings and weekends, and a one-year workmanship warranty for your peace of mind.

Nest Airwave

Tips to protect your AC Compressor

Experiencing delays with your Nest Thermostat can be frustrating, but it's essential to understand how it protects your AC compressor and learn ways to improve its efficiency.

  1. Keep AC unit area clean: Remove debris and dust from around your outdoor unit to ensure proper airflow.
  2. Schedule regular maintenance: Have an HVAC professional inspect your system, as small issues can add up and affect the compressor's lifespan.
  3. Ensure proper lubrication and pump function: Regularly check the lubricant and pump to prevent overheating and maintain efficiency.
  4. Change filters biannually: Replace your HVAC filters every six months to improve airflow and reduce strain on your compressor.
  5. Inspect wiring: Regularly check for any damaged or frayed wires to avoid potential hazards, and ensure proper electrical connections.
  6. Monitor refrigerant levels: Have a professional perform regular refrigerant checks, as low levels can lead to reduced efficiency and damage to the AC compressor.

Nest Thermostat Delayed: Conclusion

In conclusion, the “Heating is delayed” or “Cooling is delayed” message on your Nest Thermostat indicates that your device is not getting enough power to operate properly. 

This can affect your comfort and the performance of your system, as well as cause other problems with your HVAC system. 

To prevent this issue, you should consider installing a C-wire or a C-wire accessory to provide a stable and consistent power source for your Nest thermostat. 

By doing so, you can enjoy the full benefits of your smart device and avoid any delays or malfunctions.

We hope this solved the Nest Thermostat Delayed error message.


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1 Comment

  • Daniel Cuckler
    Posted October 15, 2021 at 12:15 pm

    We swapped out the nest for an Ecobee and it was rebooting. Fortunately Ecobee’s troubleshooting on the web is much better. Had our HVAC move the blower speed wire from med/low to med/high. Apparently, most units have different set speeds for the blower motor between AC and Heat. The furnace was reaching it’s high temp limit inside the unit. Since we have changed the blower speed, all is good. No more reboots on the Ecobee. Common symptoms are delay in the heat cycle or messages about the R wire being disconnected on the Nest.

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