My AC Works During the Day But Not at Night: 6 Reasons

Your AC works just fine during the daytime but not at night. It seems like an unrealistic problem. But you’re currently witnessing it, thinking about what could have gone wrong.

There are a few reasons why an AC works during the day but not at night.

One main reason could be because it has a refrigerant leaking problem. Due to this, the pressure in the coil drops. Other causes such as air temperature fluctuation (since the temperature drops at night), lack of airflow, a stuck contactor, and even a bad capacitor.

So which one of these could be your problem? Care to find out? Then, keep reading our post until the end.

Troubleshooting an AC Not Working at Night

AC not working at night is such an odd problem. One that seems like it doesn’t make any sense. It was working just fine in the heated daytime in the middle of summer.

Troubleshooting an AC

But at night, it just won’t work. Even though it’s weird, there are a few logical reasons for it. In this segment, I’ll go over the main reasons for this problem.

Faulty Refrigerant 

A faulty refrigerant could be why your AC stops running at night. Refrigerant is a necessary liquid that makes air conditioning happen. 

It sucks up the heat from the air and provides a cooling effect on it. Trouble arises when the liquid refrigerant starts to leak if you add refrigerant once or twice a month, now that it’s leaking.

This happens when the different AC parts come in contact due to vibration. It can also happen if the joints of the inner part fittings become loose. One way to look out for it is to notice if there’s any noise. 

If you hear a hissing or bubbling noise from the line, it has a leakage problem. The fact that your AC isn’t working at night is also a sign of it.

If the refrigerant keeps leaking, the pressure in the evaporator coil drops. As a result, moisture starts to freeze the coil. It only keeps increasing from that point on until it no longer functions.

It can also cause the liquid line to run cold

Solution

First, check for the signs of a leaking refrigerant. If you think the signs are relatable, turn off your AC first. Then, call for professional help.

Unfortunately, if your refrigerant leaks, it’s beyond your control now. You need to call an HVAC technician as soon as you can.

Air Temperature Fluctuation

Temperature fluctuation doesn’t affect the air conditioner much. But the temperature has to be within a particular range. Otherwise, the outdoor AC unit won’t function properly.

The temperature falls extremely low at night in some regions. This problem is more common there. When the air temperature becomes too low at night, the pressure in the system drops.

It causes your AC to freeze up.

Solution

To counter this issue, you can build a box around the outside portion of your AC. This will inhibit cold, strong winds from messing with your AC unit. 

Again if that doesn’t work, your best bet would be to talk to an HVAC professional about it. In the meantime, disconnect your AC from the power line. Fluctuating temperature can ruin your AC. 

Using Smart Thermostat

Are you using a programmable smart thermostat? It has a few default settings systems. One of them is to raise the cooling temperature of your AC unit at night.

Maybe your air conditioner stops working at night due to this default setting. 

Solution

If the default setting of your thermostat is skewed, check if there’s a hold option on your thermostat. 

Now adjust the temperatures to your necessity. Hopefully, this will solve your problem.

Lack of Air Flow

When your AC gets frozen at night, the problem is probably within the condenser. It is the outdoor unit air conditioner. Its functionality is to release the heat collected through the indoor unit.

This is related to the air flowing inside your air conditioner system. If there’s a lack of airflow, the evaporator coil freezes up. So, your AC stops working.

This is a common problem for air conditioner troubleshooting. It can cause your AC to stop at any time. But it can also be a reason for the nighttime issue.

Solution

By solving the airflow problem, the problem of AC not working at night can be fixed. 

One of the main culprits behind restricted airflow is probably the dirty air filter. Maybe it has gotten clogged. You can either choose to clean it or replace it. 

dirty air filter

However, if your air filter is clogged beyond rescue, get a replacement. Now, If you’re thinking of a replacement, you can try one of these-

Air FilterWhere To Get
Filtrete 20x20x1, AC Furnace Air FilterGrab Now from Amazon!
Filterbuy 20x20x1 Air Filter MERV 11Grab Now from Amazon!

This issue can also happen because of a faulty condenser fan. See whether it’s running on low speed. Check the AC condenser fan motor as well. If the fan blades are running slowly or making noise, the motor is the problem.

The Stuck Contactor

A contactor is a small part of your air conditioner’s outdoor unit. Its job is to provide power to the condenser fan and the compressor. It turns the air conditioner on and off.

The switch-like part of it can get stuck, causing the condenser to run continuously. If that happens, your ac will eventually freeze up. 

Solution

You can try turning off your AC at the thermostat to identify this issue.

If your outdoor AC unit is still running, the contactor is stuck. To shut off the system in this situation, turn it off from the circuit breaker. This tactic also works if your AC makes noise after a power outage.

Capacitor Gone Bad

There’s a run capacitor located inside the outdoor unit of air conditioners. Its job is to start the condenser fan and the compressor. If the capacitor becomes faulty, your AC won’t run.

So, how do we identify this problem? Notice if you hear any clicking or buzzing sound coming from the condenser. It means that the condenser fan motor is trying to start.  But I can’t do it because of the capacitor.

Solution

You can temporarily fix the issue by spinning the fan clockwise manually. Get a narrow item like a screwdriver that can fit into the grille. 

Now, try to spin it. The fan will probably start running.

A faulty capacitor will look bulged than the usual appearance. The flat top may become domed, and the oily component will start to seep through. 

These are the signs that the capacitor has reached its limit. You need a replacement right away. Here are some capacitor replacements that I’ve personally used and loved:

Capacitor ReplacementWhere To Get
The HVAC Genius 45+5 uf MFD 370/440 Volt Dual Run Round CapacitorBuy Now from Amazon!
PowerWell 45+5 MFD 45/5 uf 370 or 440 Volt Dual Run Round CapacitorBuy Now from Amazon!
MAXRUN 40+5 MFD uf 370 or 440 Volt Dual Run Capacitor for AC CondenserBuy Now from Amazon!

You can watch this video to get a clear idea about how to change the capacitor of your AC unit-

Now, if you fail to replace it by yourself, call the HVAC professional and tell them to replace the capacitor. 

All these problems mentioned above can be the reason you were looking for. However, in your case, the problem might be different. 

So, we suggest you take professional help on this matter. After all, HVAC problems are too complicated to handle if you’re inexperienced.

FAQs

How do you tell if the blower motor is bad?

If the blower motor is bad, the vents will have little airflow. You may detect weird smells due to the blower overheating. There will be strange noises as well. The energy bill will also skyrocket. Another sign is that the condenser unit works fine but the indoor unit doesn’t.

Can I use any thermostat for my AC?

You can only use a thermostat that matches your air conditioner’s system voltage. Most thermostats will work at low voltage. An electronic baseboard heating system or a  floor/wall heater uses a high-voltage thermostat. If yours isn’t one of them, you’ll probably need a low-voltage thermostat.

Why is my AC running but not cooling the house?

It’s probably because the condenser coil is clogged with dirt. The condenser fan pulls the outside air into the system through the coil. If the coil gets clogged the air won’t be passed. As a result, your ac will fail to cool down your house.

End Note

That’s all about my AC works during the day but not at night. Hopefully, now you have a clue what must have gone wrong. Whether you can identify the issue or not, call professionals to deal with this issue. 

Trying to solve it by yourself can cause further damage or void the manufacturer’s warranty. So, always take professional help.

Take care!

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