Are you dealing with a nest thermostat not blowing cold air? If so then don’t worry because this guide talks about why your nest thermostat is not cooling and the steps you can take to troubleshoot and resolve this problem
In many cases, when your nest thermostat is not blowing cold air, this is likely due to incorrect thermostat settings, dirty air filters, wrong thermostat wiring, problems with the condenser unit or a leaking ductwork system.
Before we dive into troubleshooting procedures for why your nest is now blowing cold air, let’s look at these issues as summarized in the table below.
8 Possible causes for a nest thermostat not blowing cold air
|Possible cause||The fix|
|Incorrect thermostat setting||Set your thermostat to cool|
|Thermostat delay||Wait for 5 minutes|
|Dirty air filters||Clean or replace filters|
|Wrong thermostat wiring||Check wiring, do it correctly|
|Low or leaking refrigerant||Consider recharging your system|
|Power issues with the condenser unit||Check the power ‘switching’ points for the condenser|
|Damaged ductwork||Seal off the duct system|
Let’s dive into the details of the issues shown in the table above.
Incorrect thermostat setting
Is your nest not blowing cold air? Before you start any troubleshooting procedures for your thermostat and AC system, ensure to verify that you have the correct thermostat settings on the thermostat.
The first thing you want to do is confirm that you have set your thermostat too cool and the fan is set to auto.
When your system is not set to cool, especially when you are using a heat pump system, it will not blow cold air matter how much you try to bring down the temperature settings.
Once you rule out correct thermostat setting and your system doesn’t blow cold air, you may want wit for at least 5 minutes because your system might just be in delay mode
When your nest thermostat won’t blow cold air, you might have to give it at least 5 minutes. This is because your system may just be in delay mode.
Delay mode on a nest thermostat is a feature that comes with most thermostat that prevents the HVAC equipment from coming on too quickly after turning it off or after a power outage.
After a power cut and you turn on your AC, your thermostat will prevent it from blowing cold air . This prevents the compressor from short cycling and most importantly from getting damaged.
Just give it a few minutes before you go on to troubleshoot other issues.
When the 5 minutes else’s and you have no cold air blowing out of the vents then this is the right time to consider taking a look at your air filter.
Dirty air filters
Dirty filters will cause all sorts of problems with your Nest thermostat and one of the things it will cause is non cooling of your ac.
At this point head down to the air handler and inspect the blower compartment, where the air filter is typically installed. Remove the filter and hold it up to the light.
If you can see light through the filter then it is definitely the right time for a filter replacement.
Others times, the filter doesn’t have to be too clogged, you can easily tell just by taking a good look at it and it will tell you if it needs a replacement
Replacing a clogged or dirty air filter should fix the problems. Otherwise if you believe you filter is clean and not the one that prevents your nest from blowing air, you might want to take a look at the thermostat wiring.
Wrong thermostat wiring
Is this a new thermostat installation? If so there could have been a mistake along the way of installing. Updating from a honey or any other thermostat to a nest thermostat, there are specific wires that you need to ensure they stay connected.
On the wires are the ob wires that are for the four way reversing valve.
The OB terminal is for the reverse valve that helps you heat pump to cool your ho and also to heat it when there is need. A honeywell wire will usually label this sys as the W wire and so this should go to the OB connector on the.
Other important terminals that you need to ensure are well connected are the
Y terminal; for stage 1 compressor relay
Y2 for stage 2 compressor relay
C- wire or the blue wire supplies constant power to you thermostat especially if your thermostat uses wifi
R wires: power for cooling.
To have a better understanding of your nest wiring, consider going through this guide.
Read aslo: Honeywell thermostat not blowing cold air
Power issues with the condenser unit
You should also check whether the outdoor condenser unit has a power connection.
Start by checking on the electrical breaker box for tripped switches. Check if the A/C switch is tripped and if it is reset.
Then try turning on the cooling from your thermostat, check if the outdoor unit is running and if tis not, go outside and check if the disconnect is intact.
The disconnect is an outdoor switch for your AC that is used for turning off the power to the condenser by professionals when they are doing their routine jobs. Someone may have forgotten to put it back.
If the disconnect is intact but the condenser then there could be problems with the ac contactor of the ac capacitor within the condenser.
Both the contact and the capacitor may be easily and cheaply replaced and this can solve the problem.
Low or leaking refrigerant
Another common issue that can prevent your nest thermostat from blowing cool air is a low or leaking refrigerant. This is one of the commonest reasons for this behavior.
A refrigerant is a chemical that is used in air conditioning and refrigeration systems to bring about cooling or heat( for heat pump systems). This is achieved by evaporation and condensation with the help of a compressor.
When the refrigerant evaporates, it absorbs heat from your indoor space and when it condenses in the condenser coils, it ejects the heat into the surrounding air.
Technically speaking, the refrigerant is designed to run in a closed system, where it doesn’t have to diminish.
However, with time, the system may develop leaks and the refrigerant can escape out, when this happens there won’t be cooling in your home.
The best thing to do when you suspect that your refrigerant has leaked out of your system is to call licensed professionals for help. They may also find the source of the leaks with their special detecting tools before sealing them off
Defective fan blower
You can also run down to the air handler and check if the air blower is spinning when you set your nest to cool. If it doesn’t, turn off the system from the power switch and tryp spinning it manually.
If it can spin or is having a hard time spinning, it could be defective.
Another thing you can try if you are a DIY if to test the blower motor for continuity. If there is no continuity you might just need to replace the fan blower capacitor or relays which in both cases can easily and cheaply be replaced.
Also read: AC blowing 70 degrees air
At this stage we have learned the common causes for a nest thermostat that is not blowing cold air and the possible fixes. We hope that from our guide, you are able to troubleshoot and fix your issue if not you might want to call a local pro for help.
See also AC cooling problems (External link)