AC Unit Running Outside But Not Inside: 5 Troubleshooting Steps To Fix

AC unit running outside but on inside! You will encounter this problem for several reasons. A faulty fan, frozen evaporator, and thermostat problem are the reasons that cause your AC unit to run outside but not inside.

And this air conditioner troubleshooting guide will help you to solve the issue. Therefore, we also break down why your outside AC unit is not working properly. So, read between the lines to explore the solution. 

AC Unit Running Outside But Not Inside

Why Is My Ac Unit Running Outside But Not Inside?

Is your central ac unit running outside but not inside? Then, this chapter will disclose the reasons why there is no air blowing while the outside unit is running. 

01. Fan Is Dead

A dead or defective fan is the main culprit that prevents the inside unit of your AC from functioning. 

A broken fan blade, worn-out fan motor, and frozen evaporator coil are the reasons behind a faulty fan. You can easily understand if the fan blade gets broken. An unusual noise coming out of the outside unit is an indication of a broken fan blade. 

On the other hand, the blower fan will not turn on or spin if its motor gets worn out.

How To Fix:

First off, inspect the outside unit for a broken fan blade. For this, turn off your AC first. Then, go outside to your outdoor unit. You can find the condenser fan motor and the fan mounted at the top in the center of the unit. Visually inspect the fan blade through the fan guard. If it gets cracked, you should replace it with a new one. 

On the other hand, if the fan motor gets defective, you must replace it. Follow the below steps to learn how to change the fan motor on your AC unit. 

  • Turn off the power supply to your AC unit first for safety. 
  • Remove dirt, debris, and leaves from the outdoor condenser. 
  • Then, pull out the protective grill of your air conditioner. 
  • Use a soft brush to clean the fins by removing dirt, debris, and grime. 
  • You can find the fan motor below the fins mounted to your AC with the help of wires and switches. 
  • Now, pull out the fan motor along with the wires and a few mounting bolts. Next, place a new fan assembly inside the central unit of the AC. Then, put everything back into their place. 
  • Finally, make sure you back your AC to the thermostat mode. 

02. AC Evaporator Gets Frozen

A frozen AC evaporator is also responsible for not letting your inside unit operate correctly. If the evaporator coil is freezing, your AC unit will get overheated and go to the short cycling mode. Indeed, you will get no cooling effect if the evaporator gets frosted. Typically, the unit would freeze over if you set the thermostat colder than 67 or so. 

How To Fix:

The easy fix to this problem is- just turn off your AC and wait until the evaporator thaws. You can also manually check the evaporator. Just unscrew the access door, open it, and inspect the evaporator. 

03. Thermostat Problem

The thermostat will control the entire AC system and a problem of it can simply prevent your AC from turning on. You will encounter the thermostat issue most often if you live with others. Maybe someone adjusted the thermostat, which changes the thermostat setting. Lastly, dead batteries of the thermostat will also cause your inside AC unit to not work properly. 

How To Fix: 

Firstly, ensure you set the thermostat to Cool mode. Then, set the inside temperature setting to lower than the outside temperature. Next, change the batteries of your thermostat if they are dead. If your inside AC doesn’t run after trying out these steps, you should replace the thermostat with a new one. 

04. A Clogged Air Filter

Air needs to flow through the air filter to let your AC work properly. If you don’t clean the air filter regularly, dirt, debris, and grime will nest in the filter and block it. Consequently, air can’t flow through it, which causes your inside AC unit to malfunction. 

How To Fix: 

Cleaning the air filter will be an easy fix for this issue. To do this, remove the front panel from your AC unit. You can also clean this panel if it looks dirty. Then, remove the air filters from your AC and vacuum it. Also, you can rinse it with water. Before placing them into their places, ensure the air filters get dried. 

05. Circuit Breaker Gets Tripped

A tripped circuit breaker is another reason behind a malfunctioning air conditioner. The circuit breaker will get tripped when there is a great power surge. It will occur when you run too many appliances at the same time. There will be no power if the breaker gets tripped and you can’t operate your AC. 

How To Fix:

Check the breaker box and ensure the main breaker is in the On position. If it’s not On, flip it to the On position. If you don’t get any power after turning the breaker to the On position, we bet there is a serious electrical problem. Regarding this, you should hire a certified professional to do this task for you.  

What Causes Outside AC Unit To Stop Working?

Sometimes, your outside AC unit will not function properly. Several reasons cause the outside AC unit to stop working. And we will break down those reasons in this chapter. 

Firstly, it can be the 24-Volt relay that trips the 230 Volt Line. To inspect this, turn the inside thermostat all the way down and go to the outside unit. Then, turn the power supply off to the unit (breaker box). 

Now, open the unit and check if the relay is engaging the 230-volt leads. If you are uncertain, take a wooden object and push it down on the ceramic bar that connects the contactors. If it has played, you are not activating the 24-volt relay. To verify this, turn on the 230 volts. Then, use a wooden object again to press on the ceramic bar. If it starts, there is a problem with the contactor assembly. In other words, you should replace the contactor assembly. 

Secondly, a bad capacitor or a defective fan motor is also responsible for a malfunctioning outside AC unit. 

Thirdly, a bad compressor can also be the culprit to cause your outside AC unit to stop working. Turn on your unit and see whether it trips the breaker quickly or not. If yes, we bet the compressor gets faulty. 

Therefore, a clogged condensate drain line, the emergency switch gets flipped, or thermostat issues are responsible for a faulty outside AC unit. 

We recommend you hire an HVAC expert to deal with these issues. 


Your inside AC unit will not work if the fan gets defective or the circuit breaker gets tripped. Therefore, a clogged air filter, a frozen evaporator, and a faulty thermostat also cause your inside AC unit to malfunction while the outside unit is running properly. Follow the troubleshooting steps we mentioned to fix this AC problem. Otherwise, you should hire a certified HVAC expert to solve this issue for you. 

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