Nest Thermostat Not Turning on AC Compressor [Solved]

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This troubleshooting guide is for you if you are dealing with a Nest thermostat not turning on your AC compressor. It can be pretty frustrating to discover that your ac compressor can’t turn on to cool your living spaces, which could leave you feeling uncomfortable.

Some reasons why your Nest thermostat won’t turn on your ac compressor include:

  • Incorrect thermostat settings
  • Problems with power
  • You have an ac capacitor that is defective
  • Your ac contactor is not working fine.
  • Your compressor died (In the worst-case scenario)

Read also: Fan Kicks on But Compressor Not Working [Solved]

Why is My Nest Thermostat Not Turning on AC Compressor?

Let’s jump right into issues that can prevent your nest thermostat from turning on your ac compressor.

Incorrect Thermostat Settings

If your Nest thermostat is not set to ‘cooling’ mode, it won’t turn on your compressor. Sometimes your thermostat can be on ‘cooling,’ but if your temperature is set above your current temperature reading, your ac won’t start.

To start your ac compressor, set the point below the current room temperature reading.

To completely rule out thermostat issues, check how your thermostat was programmed. Ensure it was correctly programmed. If it wasn’t, try reprogramming your thermostat so that your ac can start cooling.

Problems With Power

Another possible reason your ac compressor won’t start with a nest thermostat is that there could be a power cut to your outdoor unit. Your outdoor condenser unit can be cut off from power if

  • The circuit breakers tripped
  • If the power switch(disconnect) was pulled out from its position
  • Your ac contactor is defective

Tripped circuit breakers

Tripped circuit breakers could be why your Nest thermostat is not turning on your ac compressor. Occasionally, breakers can trip due to a compressor lockout or a power surge. When that happens, the problem can easily be fixed by resetting your circuit breakers.

If the breaker trips twice, call a licensed HVAC technician to come and do a thorough test on your ac system for any other issues.

Disconnect Pulled Out

Other power issues that could prevent your ac compressor from turning on include a ‘disconnect’ that is switched off. A ‘disconnect’ is a device that cuts power when maintenance or other works are done on your ac outdoor unit.

If you have had someone do some work on your HVAC system, they might have disconnected it and forgotten to put it back. You can check it to rule it out.

Other times, your ‘disconnect’ can also be equipped with a fuse. If yours has a fuse, check that the fuse is not blown out. If there is no noise from your outdoor unit when you turn it on with your thermostat, you’ll need to check if your AC contactor is working.

Bad AC Contactor

A contactor powers up your outdoor unit when there is a call for cooling or heating. However, though rare, this device can become defective. If it becomes defective, your AC compressor won’t turn on.  If you try turning on your ac from your thermostat and there is no sound from your outdoor unit, your ac contactor might be defective.

How do I know if my ac contactor is defective?

Open your ac unit cover with a screwdriver. A contactor looks like one in the picture below.

bad ac contactor

You can either have a dual pole or a single pole contactor. Try manually contacting the two contactor plates (You can turn on your ac at this point.) If your compressor and fan start, your problem was with a contactor. If not, check your AC capacitor.

Bad AC Capacitor

A bad or failed ac capacitor is among the most typical reasons for an ac compressor that is not turning on. Capacitors store energy and supply the compressor with the needed energy to start running.

If your capacitor is dead, your compressor won’t start when you try turning it on with your thermostat.

Sometimes it’s easy to spot a capacitor that has failed. It will have a swollen top. Other times you’ll need a multimeter to test it for continuity. The bottom line is that if your capacitor is dead, you’ll need to replace it with a working one.

These days ac capacitors are readily available, and you can get one online. Take note of the model information to ensure you buy the suitable model.

Also read: AC Compressor Working but Not Cooling [Solved]

Dead Compressor

The problem you probably don’t want to hear about is a dead ac compressor. If you have had that compressor for a long time, like ten years, it’s possible that it has served its purpose for your home and needs a replacement.

Even though compressors a designed to work throughout the life of your air conditioner, they can die when you least expect them to. When that happens, you’ll have to replace your compressor or replace the whole ac system. You can get quotes for both options.

Suppose your think replacing your ac compressor will be costly, which in most cases is. In that case, I’ll recommend you replace the whole ac system specifically if the cost of replacing your compressor is more than half the cost of replacing the whole ac unit.

Things you can do to increase the life of your ac compressor

  1. Regular maintenance: having a schedule and regular HVAC maintenance will keep your heating and cooling systems working efficiently and with fewer problems. Regular maintenance will also prevent unexpected and costly HVAC breakdowns.
  2. Replacing your filters on time. Clean air filters help your HVAC system to work without strain. But if your air filters stay clogged, this can negatively affect many components of your HVAC system, including your compressor. Typically, air filters should be cleaned or replaced at least once in 2 months.

Need A New Nest Thermostat? These are the Newest Models

SaleBestseller No. 1
Google Nest Learning Thermostat – Programmable Smart Thermostat for Home – 3rd Generation Nest Thermostat – Works with Alexa – Stainless Steel
  • No more programming: With Auto-Schedule, the Google Nest Learning Thermostat learns from you and programs itself.
  • Home/Away Assist: don’t heat or cool an empty home. Home/Away Assist adjusts the temperature after you leave.
  • Remote control: Control your thermostat from anywhere using the Nest app.
  • Know more, save more Check your Energy History to see how much energy you use and why.
  • Look for the Leaf: The Nest Leaf appears when you choose a temperature that saves energy.
SaleBestseller No. 2
Google Nest Thermostat – Smart Thermostat for Home – Programmable Wifi Thermostat – Snow
  • ENERGY STAR certified smart thermostat for home that helps you save energy and stay comfortable
  • The Nest Thermostat is designed to work without a C wire in most homes, but for some systems, including heating only, cooling only, zone controlled, and heat pump systems, you’ll need a C wire or other compatible power accessory
  • Nest Thermostat turns itself down when you leave, so you don’t waste energy heating or cooling an empty home
  • Programmable thermostat that lets you create an energy efficient schedule in the Google Home app on your Android or iPhone
  • Remote control lets family members change the thermostat temperature from anywhere on a phone, laptop, or tablet[1]
SaleBestseller No. 3
Google Nest Learning Thermostat – Programmable Smart Thermostat for Home – 3rd Generation Nest Thermostat – Compatible with Alexa – Stainless Steel-Renewed
  • Google Nest Learning Thermostat – Programmable Smart Thermostat for Home – 3rd Generation Nest Thermostat – Works with Alexa – Stainless Steel-Renewed
Bestseller No. 4
Google Nest Temperature Sensor 3 Pack – Nest Thermostat Sensor – Nest Sensor That Works with Nest Learning Thermostat and Nest Thermostat E – Smart Home
  • Works with compatible Nest thermostats [1]; the sensor tells the thermostat what the temperature is in the room where it’s placed and the thermostat uses that reading to control when the system turns on or off to keep that room the temperature you like
  • Put different temperature sensors in different rooms, like the baby’s room or living room
  • Control your Nest sensor in the Nest app; set a schedule and choose which room to prioritize when [2]
  • Compatible with the Nest Learning Thermostat and the Nest Thermostat E [1]
  • The Nest Temperature Sensor is easy to set up; just hang it on the wall or place it on a shelf
SaleBestseller No. 5
Google Nest Learning Thermostat – 3rd Generation – Smart Thermostat – Pro Version – Works With Alexa
  • This specific product is intended for Professional Installers only and not to be sold direct to consumers. Please see other consumer facing listing for more color options
Bestseller No. 8
Google Nest Learning Thermostat 3 Pack (T3007ES) 3rd Gen Stainless Steel
  • 3x Google Nest Learning Thermostat 3rd Gen Stainless Steel
  • It has new rings and a big, sharp display
  • Nest shows you how much energy you use every day in Energy History and every month in your Home Report
  • IN THE BOX: Base – Trim Kit – Labels Nest Screwdriver
  • BUNDLE INCLUDES: 3x Google Nest Learning Thermostat 3rd Gen Stainless Steel
Bestseller No. 9
Nest T4001ES Wi-Fi Programmable Thermostat E
  • This Certified Refurbished product is manufacturer refurbished, shows limited or no wear, and includes all original accessories plus a 90-day limited hardware warranty.
  • Finish: White
  • Manufactured By: Nest
  • Diameter: 3.3 in.
Bestseller No. 10
Nest Learning Thermostat – 2nd Generation T200477
  • Auto-Schedule: Nest creates a personalized schedule based on the temperature changes you’ve made.
  • Auto-Away: Nest automatically turns itself to an energy-saving temperature when you’re away
  • Remote control: Connect your Nest thermostat to Wi-Fi, download the free Nest Mobile app, and change the temperature from anywhere.
  • Nest Leaf: Nest will show you when you’re choosing a temperature that’ll help you save. Look for the Leaf every time you turn the ring.
  • Language is in English or French

Final Thought

We hope this guide on dealing with a Nest thermostat not turning on ac compressor has been helpful. If you still can’t figure out how to resolve the problem after reading this article, it’s best to call your local HVAC technicians. They should be able to fix this for you in no time. Thanks for reading.

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