Why Is My Honeywell Thermostat Not Turning On The AC? (Revealed!)

As the temperature rises, it’s important to have a functioning air conditioning system to keep your home or office cool and comfortable. But what if you notice that your Honeywell thermostat isn’t turning on the AC?

This can be a frustrating experience, especially during the hot summer months. A thermostat is an essential component of your HVAC system, and when it’s not working properly, it can affect the performance of your AC unit.

In this blog post, we’ll discuss some of the common issues that can cause a Honeywell thermostat to not turn on the AC.

We’ll provide step-by-step instructions on how to troubleshoot these issues and offer solutions to fix them. By the end of this post, you’ll have a better understanding of how to identify and fix the problem, so you can enjoy a cool and comfortable living or working space.

Here are some common issues and their solutions:

Potential Cause	Troubleshooting Steps
Power source issues	Check the circuit breaker and fuse, reset the thermostat
Dead or low batteries	Replace batteries
Wiring issues	Check the wiring for damaged or loose connections, and tighten or replace them as needed

Common causes & their solutions

Page Contents

Check The Power Source

The first step in troubleshooting a Honeywell thermostat that’s not turning on the AC is to check the power source.

A power source issue is a common cause of a malfunctioning thermostat, so it’s essential to rule out this possibility before moving on to other potential causes.

To check the power source, follow these steps:

Check the circuit breaker: The first thing you should do is check the circuit breaker. A tripped breaker can prevent the thermostat from receiving power. Locate your circuit breaker box and check for any tripped breakers. If you find one, flip it back on and check if the thermostat starts working again.
Check the fuse: If your thermostat is wired to a fuse box, check the fuse to ensure it’s not blown. A blown fuse can also prevent the thermostat from receiving power. Replace the fuse if necessary and check if the thermostat starts working again.
Check the wiring: Check the wiring connected to the thermostat and make sure it’s not damaged or disconnected. Loose or damaged wiring can prevent the thermostat from receiving power.

If the power source isn’t the issue, the next step is to check the batteries.

Check the Batteries

Ensure that your batteries are working fine. — Making sure that the battery is working fine

Honeywell thermostats use batteries as a backup power source in case of a power outage.

If the batteries are dead or low on power, the thermostat may not turn on the AC. Checking the batteries is a quick and easy process that can help solve the problem.

To check the batteries, follow these steps:

Remove the thermostat cover: Remove the cover of the thermostat to access the batteries. Some thermostats require you to press a tab or release a latch to remove the cover.
Check the batteries: Check the batteries and make sure they’re not corroded or leaking. If the batteries are corroded or leaking, remove them and clean the battery contacts with a soft cloth. If the batteries are low on power, replace them with fresh ones.
Reinstall the cover: After checking or replacing the batteries, reinstall the thermostat cover and check if the thermostat starts working again.

If the batteries are not the issue, it’s time to move on to the next potential cause of the problem.

Check The Wiring

Nest Thermostat Wires — Sometimes an issue with the wiring is the reason your thermostat isn’t working properly

If the power source and batteries are not the issues, the next step is to check the wiring of your Honeywell thermostat.

Damaged or loose wiring can prevent the thermostat from turning on the AC.

To check the wiring, follow these steps:

Turn off the power: Before you start, turn off the power to the thermostat and the AC unit. This will prevent any electrical accidents.
Remove the thermostat cover: Remove the cover of the thermostat to access the wiring. Make sure to note the location of each wire and label them if necessary.
Check the wiring: Check each wire and make sure they’re not damaged or loose. If you see any damaged or loose wire, tighten it and replace the damaged wire.
Reinstall the cover: After checking and fixing the wiring, reinstall the thermostat cover and turn the power back on.

If the wiring isn’t the issue, it’s time to move on to the next potential cause of the problem.

Check The AC Unit

If the thermostat is working properly and the AC unit is not turning on, there may be an issue with the AC unit itself.

There are several potential causes of this problem, including a clogged air filter, a tripped circuit breaker, a frozen evaporator coil, or a malfunctioning compressor.

To check the AC unit, follow these steps:

Check the air filter: A clogged air filter can restrict airflow and prevent the AC unit from turning on. Examine the air filter and substitute it with a clean one if it’s clogged or dirty.
Check the circuit breaker: Check the circuit breaker and make sure it’s not tripped. If it is, flip it back on and check if the AC unit starts working again.
Check the evaporator coil: Check the evaporator coil for frost or ice buildup. If the coil is frozen, turn off the AC unit and let the ice melt. Once the ice has melted, turn the AC unit back on and check if it starts working again.
Check the compressor: If none of the above solutions work, there may be an issue with the compressor. Call a professional to identify and resolve the issue.

By following these steps, you can identify and fix the most common causes of a Honeywell thermostat not turning on the AC. If none of these solutions work, it’s best to contact a professional HVAC technician for assistance.

Check the Thermostat Settings

Another potential cause of a Honeywell thermostat not turning on the AC is incorrect thermostat settings.

Because if the thermostat is set to the wrong mode or temperature, it can prevent the AC unit from turning on.

To examine the thermostat settings, take the following steps:

Check the temperature setting: Make sure the thermostat is set to a temperature that’s lower than the current room temperature. If the thermostat is set to a higher temperature, the AC unit won’t turn on.
Check the mode setting: Make sure the thermostat is set to the correct mode. If your thermostat has a “cool” mode, make sure it’s selected. If the mode is set to “heat,” “off,” or “auto,” the AC unit won’t turn on.
Check the fan setting: Make sure the fan is set to “auto.” If the fan is set to “on,” it will run continuously and prevent the AC unit from turning on.
Check the schedule: If your thermostat has a scheduling feature, make sure it’s set to the correct settings. If the schedule is set to turn off the AC unit during certain times of the day, it won’t turn on during those times.
Check for any programming issues: If your Honeywell thermostat has programmable settings, make sure they are set correctly. Review the programming settings and ensure they match your preferences.

Learn more about Honeywell Thermostat not working

FAQs

Why is my Honeywell thermostat not turning on the AC?

There could be several reasons why your Honeywell thermostat isn’t turning on the AC, including issues with the power source, batteries, wiring, AC unit, or thermostat settings.

How do I check if the power source is the issue?

To check if the power source is the issue, make sure the circuit breaker is on and the fuse isn’t blown. You can also try resetting the thermostat by turning the power off and back on again.

How do I check if the batteries are the issue?

To check if the batteries are the issue, remove the thermostat from the wall and check the batteries. If the batteries are dead or low, replace them and check if the AC unit turns on.

How do I check the wiring of my Honeywell thermostat?

To check the wiring, remove the thermostat cover and check each wire. Make sure they’re not damaged or loose. If there are any loose or damaged wires, tighten them up or replace them in case of damaged wires.

How do I check the AC unit?

To check the AC unit, make sure the air filter is clean, the circuit breaker is not tripped, the evaporator coil isn’t frozen, and the compressor is working. If none of these solutions work, contact a professional HVAC technician.

Conclusion

A Honeywell thermostat not turning on the AC can be frustrating, but it’s important to identify and address the issue to ensure your home stays cool and comfortable.
By following the steps outlined in this blog post, you can troubleshoot and fix common causes of the problem, including checking the power source, batteries, wiring, AC unit, and thermostat settings.
It’s worth noting that some issues may require the assistance of a professional HVAC technician.
If you’ve tried all of the troubleshooting steps and the problem persists, it’s best to contact a professional to diagnose and fix the issue.
Remember to always prioritize safety when working with electrical systems.
Turn off the power before checking the wiring or making any repairs, and wear protective gear when necessary.
By following these tips and staying vigilant about the health of your Honeywell thermostat and AC unit, you can ensure your home stays cool and comfortable all summer long.