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Seeing a “Delayed until” message is quite common on Nest Thermostats.

A delayed start of cooling is usually a protective measure by your thermostat or HVAC system and is perfectly normal. But when the usually short delay message doesn’t disappear, it may hint at a bigger problem to investigate.

C-Wire Additional Power Options
Wireless C-Wire Sender and Receiver
Power Nest from a local outlet

At SmartHomePerfected we always advise readers not to undertake any work they are not competent in performing and if in any doubt, it is best to seek the assistance of a professional.

Low power going to your thermostat

Your Nest thermostat is capable of a lot more functions than your old thermostat. To perform these functions, it needs more power to run. The Nest thermostat has an integrated rechargeable battery.

In some cases, this battery can drain too fast, especially with operations like Wi-Fi connectivity, motion sensors and other smart functions. If the thermostat doesn’t get enough power, you can experience problems such as intermittent heating, cooling or inconsistent fan operation.

The C-Wire

Officially, the Nest thermostat can operate without a C-wire. It does this by drawing a charge when the heating and/or cooling system is activated. Sometimes, however, it can not draw enough charge from these systems, resulting in problems like the “Delayed” message. 

To get your AC back up and running, you will need to check the C-wire on your Nest thermostat. Pull out the thermostat’s display and look at the panel labeled C. Here is where a blue wire needs to be installed if you are having low power issues.

Purpose of the C-Wire and the internal battery

Usually, your nest Nest thermostat gets enough power from your system. It draws power from the wire connected to your heating (Rh) and/or cooling unit (Rc).

The problem with this setup is that the thermostat doesn’t get continuous power. The power only flows when the wires are “switched” on, like when heating is activated.

Low Power Impact

You’re able to check the current voltage of your internal battery through the display. For some specific actions, a certain voltage is required to activate them. When the voltage falls, some features like Wi-Fi, software updates, or motion sensing cannot function. In lower voltages, the Nest thermostat will also preserve the battery and disable the screen.

This is where the C-wire is important. The C-wire helps your Nest thermostat get continuous power. With a C-wire, the electricity has a path to flow through without waiting for the wires to be switched on.

How to provide a C-Wire to your Nest Thermostat

If you don’t currently have a C-Wire coming from your furnace and surfacing behind your thermostat you have a few options.

Hardwire a C-Wire or use a Common Maker

Installing a C-wire involves connecting both ends to your HVAC system (typically the furnace) and your Nest thermostat. It is recommended that you turn off power to the equipment during installation.

This is potentially a big job as the wiring between your furnace and thermostat is likely plastered over and in the walls. It may be worth consulting a local professional on this installation work.

Alternatively, you can wireless connect a C-Wire via a sender and receiver, such as the Fast-STAT.

The device has both a sender wired to the thermostat in the wall and a receiver installed at your furnace.

Install a C-Wire Adapter

If you’re missing the needed C-wire, you have the option to use a C-wire adapter. Such adapters like this one are easy to install and tested with the Nest thermostat. 

They are essentially plugged into an outlet nearby and then wired directly into the Nest thermostat to resolve the Delayed message. The wire itself could be chased up the wall to remove any unsightly exposed wirework.

Your C-wire adapter will usually include a manual for instructions. Many of these have easy steps to follow.

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 install 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.

There are some things to consider beforehand:

  1. You lose some fan functionality by repurposing the G-wire. You won’t be able to use it on its own or in “fan-only” mode.
  2. Check that the fan isn’t connected with any other equipment.
  3. A zone panel would make this option unfeasible.
  4. A jumper cable might need to be connected to the empty G-terminal and Y-terminal.

Protecting your AC Compressor

Thermostats help you easily control and regulate your heating, ventilation, and air-conditioning (HVAC) system. The AC compressor is one of the main components in your system. The delay function of your thermostat prevents short cycling of your AC equipment. This helps protect the equipment from unnecessary wear and tear so you get a longer lifespan.

Regular maintenance of your AC system goes a long way to preserve it. Small problems with the system add up to reducing the AC compressors lifespan.

Here are ways to not just preserve your compressor, but also save you money in the long run:

  1. Keep the AC unit area clean
  2. Regular clean up and maintenance check
  3. Lubricant and pump checkup
  4. Replace the filters around twice a year
  5. Wiring checks
  6. Refrigerant checks


While a Nest thermostat delayed message sounds like a problem, it is a normal function of your thermostat and AC system. When it becomes irregular, too long, or barely produces any change to temperature there may be a bigger issue at play.

Check out the C-wire on your Nest thermostat and ensure enough power is getting to your device. Also, ensure you regularly maintain your AC unit to increase its lifespan.

We hope this guide helps and feel free to leave a comment below!

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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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