Honeywell Thermostat Won't Turn On AC: How To Troubleshoot

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When my cousin comes over to visit, her kids love to play on the display panel of my Honeywell thermostat when they have no clue what it does.

I always knew this constant roughhousing would catch up to me one day, and a few days back, it happened.

My thermostat had trouble turning the AC on. When your Honeywell thermostat fails to function properly, it not only affects the heating and cooling system of your home but can also make you pay a pretty hefty charge in utility bills.

I realized I had to find a way to fix it immediately. So I went through a number of articles and videos online and finally found a solution.

Your Honeywell thermostat may fail to turn your AC on at times. The easiest way to fix it is to reset your thermostat.

Other common methods include replacing your batteries, checking your wiring, and cleaning the air filter associated with your Honeywell Thermostat.

What Model of Thermostat Do I Have?

The fastest way to find the model of your thermostat is by looking at the thermostat ID card.

If you don’t have the product ID card, you can find it by removing the device from the wall plate.

You can pull most models right off the wall instantly. After detaching it, flip it over to find the model number printed on the back of the case.

The number is preceded by the letters TH, T, RTH, RCHT, CT, TL, or RLV.

Common Fixes When Your Thermostat Cannot Turn on The AC

Now that you have figured out which model of Honeywell thermostat you are using, let me walk you through some common methods to troubleshoot your Honeywell thermostat not cooling.

Reset The Thermostat To Factory Settings

The steps involved in resetting your Honeywell thermostat may differ according to the model that you use.

Scroll down to the model that you own and follow the procedure given below.

Honeywell 4000 series:

After making sure the device is ON, press and hold the option named ‘Program.’

Using a paperclip or a similar pointed object, press the reset button for about one to two seconds and then release the ‘Program’ button.

Honeywell 6000 series:

When your device is ‘ON,’ press and hold the ‘Fan’ button followed by the ‘Up’ arrow button, hold these buttons for about 5 seconds before releasing.

Press the button on the bottom left until the number on the display panel changes to ‘39’.

Next, press the ‘Down’ arrow button until you see ‘0’ and then press ‘Done.’

The thermostat has now been reset.

Honeywell 7000 series:

Switch off the thermostat and then cut off the power to your device. Now, remove the thermostat from your wall plate.

You will find 2x AAA Alkaline batteries. Remove them and then insert them in the opposite direction for about 5 seconds.

Now put the batteries the right way, which should turn on the display. Finally, switch on the power after you fix your thermostat on the wall plate.

Honeywell Lyric T family

Touch the ‘Menu’ button and scroll down until you see ‘RESET.’ Tap on ‘Select’ and choose ‘Yes’ to complete the reset.

You will return to the reset sub-menu if you tap on ‘No.’

Honeywell 8000 series

Press’ System’ on the screen and press and hold the blank button in the center for 5 seconds.

Now select ‘Reset to factory settings.’ Now your thermostat has been reset.

Honeywell 9000 series

Press the ‘Menu’ button and navigate to ‘Preferences.’ Scroll down to ‘Restore to factory default’ and tap ‘Yes.’

Please note that you will have to set your schedules irrespective of the model and re-adjust clock times once you reset your thermostat.

Replace Batteries If You Haven’t Yet In A Long While (selected models only)

To change the batteries on your thermostat, (if your model uses batteries).

1. Go to the circuit breaker and turn the power ‘Off.’
2. Detach your thermostat from the wall plate.
3. Remove the old batteries and insert the new ones.
4. Now attach your thermostat to the wall plate and switch the power back ‘On.’

Check Connections And Wiring For Any Damage

To check if your wiring is intact, remove the thermostat face or body to expose the thermostat wires.

You will find a white and a red wire. Connecting these should turn your thermostat ‘On.’

If your heating system turns ‘On’ when you connect the wires, the problem lies with the thermostat.

First, check if your thermostat is set above the room temperature.

If connecting the red and white wires did not do the trick, there might be an issue with the thermostat wires.

It is better that you not test the integrity of your thermostat wires yourself, keeping in mind how dangerous handling the AC mains supply is. Instead, call a professional and get their help.

Replace the Air Filter if it is Clogged

A clogged air filter will prevent air from circulating through the vents, which will, in turn, cause trouble with your air conditioning. As a result, your AC could leak or get overworked.

To prevent damage to your AC in the long run, you need to check and clean your air filters routinely.

This helps them to run efficiently and ensures a longer lifespan.

Typically, you need to clean the air filters every few months or if you find anything gray or ashy-looking on the duct side of your filter.

Contact Honeywell Support if nothing else works

If you are sure that none of the above reasons are causing the issue with your Honeywell thermostat, it is best to contact Honeywell Support.

Not being able to fix the temperature in your home can be stressful, especially on a hot day.

However, with these common and effective solutions, your air conditioning will be up and running in no time.

If you weren’t able to diagnose the issue, you could always turn to Honeywell support.

I would also like to advise against playing around with the wiring in your home too much because safety comes first!

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Frequently Asked Questions

How do I reset my Honeywell air conditioner thermostat?

You can easily reset your thermostat by removing the batteries or selecting the option from the menu.

The process varies depending on the model. So, it is best to refer to your user manual or the official website.

Can the thermostat cause the AC not to work?

Yes, your AC might not work even when it is not damaged due to issues with your thermostat. However, you can try resetting the thermostat to fix the issue.

Do AC units have a reset button?

Most AC units have a reset button on them. You will need to find the AC manual to locate the reset button. If your AC does not have a reset button, you can always reset it manually.