The AC fan should always be spinning. If the AC unit is turned on and the outdoor condenser AC fan is not spinning, you have a problem. This is quite a frequent problem with air conditioners, especially during summer.
Here are just a few examples of how homeowners phrase this problem:
- “My air conditioner fan is not spinning. What is wrong?”
- “Outside AC unit fan not spinning and it’s hot. What should I do?”
- “Outside AC unit fan spinning slow. It’s not spinning fast enough. Should I can an HVAC professional?”
The most frequent problem we encounter is the AC condenser fan not running even when the air conditioner (central AC, mini split, etc.) is turned out. In most cases, the fan that is ‘broken’ and doesn’t even turn on is the outdoor condenser fan.
Needless to say, you can’t run the air conditioner if the AC fan is not spinning. The first thing you should do is to turn the AC off.
Luckily, all problems associated with the AC fan not turning on the AC unit can be fixed (bad capacitor, fan motor problems, tripped breaker, AC belt issue, airflow restrictions).
If you were to call an HVAC professional, he or she knows exactly which 6 things to check in this situation (following the HVAC playbook).
You can follow these exact 6 steps yourself to figure out what is wrong with your condenser AC fan and fix it.
To help everybody out, we will look at all 6 culprits that prevent the AC fan from turning on and spinning. HVAC professionals go one by one, eliminating the causes of the AC fan not spinning, and, once they have diagnosed the culprit, fix the broken AC fan.
This is exactly what we can do as well. In many cases, you can fix an air conditioner fan not spinning yourself just by following this process. Let’s start by looking at which fan is not spinning, and following up with the 6 reasons why the AC fan is not turning on:
Causes Of Air Conditioner Fan Not Spinning (Or Even Turning On)
Almost all air conditioners have two fans, namely:
- Indoor evaporator fan. Mini split AC units, for example, have an indoor fan located in the air handler. This fan produces indoor airflow.
- Outdoor condenser fan. Central air units and mini splits have a condenser fan located in the outdoor unit (big white box outside). The outdoor AC fan produces outdoor airflow.
It is important to understand that both indoor and outdoor airflow is essential for an air conditioner to work. It’s like lungs; an indoor fan inhales the air and the outdoor exhales the air.
In most cases (more than 80%), we have a problem with the outdoor condenser fan not spinning. If that fan is not spinning or doesn’t even turn on, you cannot use such an air conditioner.
If you don’t want to be left sweating in the summer, it is essential for you to:
- Figure out why the AC fan is not spinning.
- Fix (or replace) the outdoor condenser fan.
As we have mentioned above, the HVAC playbook outlines 6 things that can cause AC not to function properly. Let’s go one by one (HVAC professionals do exactly this as well) and see what is causing the AC fan from turning on and spinning, and how to fix an AC fan not spinning:
1. You Have A Bad Capacitor (Most Common Issue Causing AC Fan Not Spinning)
A dead capacitor is by far the most common reason why the condenser AC fan stops working. This is a culprit in more than 30% of all ‘central air fan not spinning’ issues.
AC capacitor is a cylindrical device you will find in the outdoor unit. It’s about the same size as your hand, or a bit smaller. There are many different capacitors air conditioners have and all of them can go bad at some point in time (most of them have an expected lifespan of about 20 years).
There are 2 different capacitors that are responsible for the outside AC fan not turning or spinning:
- AC fan motor start capacitor. This capacitor sends an energy signal to the fan motor. When the fan motor receives this signal, it turns on. If you have a bad start capacitor, the air conditioner fan won’t turn on since it doesn’t receive the signal that it should turn on.
- AC fan motor run capacitor. This capacitor is responsible for sending continuous signals to the fan motor that tells the fan to ‘keep spinning’. If you have a dead run capacitor, the AC fan motor won’t get that signal, and it will stop spinning the fan blades.
You can diagnose which AC fan capacitor is bad by measuring the power signal that should be coming from the capacitor. You should use a wattmeter for this. When you turn on the AC, you should see an energy spike from the start capacitor. You should also be seeing wattage coming from the run capacitor.
If you don’t see any wattage, that means you have a bad capacitor that is causing the AC fan to not turn on (no spike wattage from the start capacitor) or spinning (no continuous wattage from the run capacitor).
Solution: In all cases of a bad capacitor, the fix is the same. You have to replace the AC fan capacitor.
First, you will have to determine which capacitor is dead (either start or run capacitor). Once you figure out that, you have to get an adequate capacitor replacement. The best idea here is to check which capacitor you have and buy exactly the same one. Condenser unit AC fan capacitor cost anywhere between $100 and $400 (with professional installation).
You can replace the AC capacitor yourself (if you have some technical skills) or call an HVAC professional to do it. Of course, professional AC capacitor replacement does incur extra costs. In most cases, however, homeowners prefer calling a professional to do the job (at the end of this article, we outline how to find the best local HVAC professionals).
Once you replace the dead capacitor, you should see the outdoor AC fan turning on and spinning normally again.
If the bad capacitor is not the issue causing the AC fan not spinning, here is what you check for next:
2. Broken Fan Motor (Most Expensive Issue That Causes AC Fan From Spinning)
If you check the outdoor AC unit and see that the AC fan is not spinning, your only wish should be this:
“God, I hope something is not wrong with the fan motor.”
The fan motor is responsible for running the air conditioner fan. Over time fan motors can burn out. You can partially prevent this by regular AC maintenance, not overworking your AC, and so on. However, if you detect that something is wrong with the fan motor – preventing the AC fan from spinning – you are in for quite an expensive fix.
Solution: Burnt-out fan motor issues are notoriously expensive to fix. Namely, if you have a bad motor, you only have two options to fix the problem:
- Replace the motor. You have to find an adequate fan motor replacement. These fan motors cost anywhere from $300 to $1,000 and they require a professional installation (which is extra).
- Replace the whole air conditioning unit. With smaller and older central AC units finding out a broken fan motor might just be the excuse you need to buy a new air conditioning system. That’s because replacing a fan motor on an older unit is quite expensive; in some cases with 15+ year old units, it’s best to avoid the AC motor replacement costs and get a new system.
An AC fan motor is generally expected to last for about 12 years. That’s why a bad fan motor is a frequent reason for condenser fan not spinning in older units.
This is the single most expensive fix for a bad AC fan. If you (hopefully) have a working fan motor, you should proceed to check these things out:
3. Tripped Circuit Breaker (Lack Of Power Supply Prevents AC Fan From Spinning)
Compared to a bad capacitor or burnt-out fan motor, a tripped circuit breaker is a piece of cake.
If you overload the AC unit or if the AC unit becomes overheated, chances are that it will trip a circuit breaker.
All adequately installed AC units follow the NEC 80% rule (you must not load the breaker more than 80% of its capacity). You can read more about what breaker size you need for air conditioners here.
However, when the outdoor temperatures are extremely high (above 110°F, for example), the resistance in the wires is increased. According to Ohm’s law, higher resistance will cause more amp draw (increase in current) at the same voltage (220-240V, for example).
As a result, the air conditioner can trip a circuit breaker. When that happens, the power supply to the AC fan motor will be cut and we will see that as AC fan not spinning.
Solution: Simple. Just flip the switch in the circuit breaker box back on. You can fix this AC fan not the spinning issue yourself; no need to call an HVAC professional for assistance.
The circuit breaker was tripped as an acute surge of current. That means you can safely flip the circuit switch since the conditions that caused it – extremely high temperatures – are not relevant anymore.
This is the easiest way to fix an outside AC fan not spinning. After you switch the circuit breaker back on, the AC fan should start spinning again.
4. AC Fan Belt Issues (Broken Or Slipped Fan Causing AC Not Spinning Or Spinning Slow)
If the AC fan is not rotating as it should, the problem might include an AC fan belt issue. An AC fan belt is basically a belt that connects the fan motor and the AC fan; it transfers the mechanical work to the fan.
The belt can malfunction. Namely, if that happens, we can see these two scenarios:
- AC fan belt is broken. That means that the fan motor is working as it should but it cannot transfer the mechanical work to the fan. The end result is that the AC fan is not spinning even when the air conditioner is turned on.
- AC fan belt has slipped. If the belt is not broken – it just slipped off the axis – you will see no or less mechanical work being transferred to the air conditioner fan. As a result, you may see that the AC fan is not spinning or the AC fan is spinning slower than it should.
Solution: If the belt has just slipped, you simply have to put it back on the axis, and the fan will start spinning faster. If the belt is broken, however, you will have to replace it. These serpentine belts are quite inexpensive, costing anywhere from $25 and $75.
You can replace the AC fan belt yourself. Just make sure the AC unit is turned off. After the belt has been replaced or put back on the axis (if it slipped), you should see the air conditioner fan working as it should again.
5. Capacitor Contactor Is Bad (AC Fan Cannot Spin)
In limited cases, the bad capacitor itself is not the issue; it’s the capacitor contactor.
The contactor that may cause the AC fan to prevent from spinning is located in the outdoor unit, next to the capacitor. It is a small switch that can go bad in older units.
If this happens, the fan will stop spinning or will spin in short bursts – the fan starts and stops spinning – even if the capacitor, compressor, fan motor, and everything else work just fine.
Without the working AC contactor, the signal relay to the fan will be obstructed. With a ‘misbehaving’ contactor, that message will go through for a few seconds; this can cause the fan to start and stop quickly afterward.
What to do if you have a bad contactor preventing the AC fan from spinning?
Solution: You will have to either attach the contactor tightly or replace the contactor. On your own, you can try to fix the contactor to be in contact with the capacitor. If that doesn’t work, the contactor is dead and you will have to replace it.
Bad contactors are usually replaced by HVAC professionals. It seems like a small thing but a lot can go wrong if you want to DIY AC contactor replacement.
6. Airflow Restrictions (Dirty Air Filters Can Cause AC Fan From Spinning In Limited Cases)
Restricted airflow can cause all sorts of problems in the air conditioner. There are also several causes of why exactly the airflow is limited or even non-existing.
The first thing you will notice is not that the AC fan stopped spinning. Most homeowners notice that their AC unit starts to freeze up. You can read more about window AC units freezing up here, for reference.
Eventually, however, this icing up will put an unnatural load on the AC fan. As a result, the AC fan will shut down and stop spinning.
Solution: The easiest way to fix this is to clean or replace the air filters. This is the most common culprit for AC airflow restrictions. If you have already done that and it didn’t help, it’s best to call an HVAC professional.
There are several reasons why the airflow can be restricted. It’s quite a complex issue best left to the professional.
How To Contact A HVAC Professional To Fix Condenser AC Fan Not Spinning:
As we have seen, there are some issues that stop the AC fan from working that you can fix yourself (#3 tripped breaker, #4 belt issues).
Others like #1 capacitor issues, #2 broken fan motor, #5 bad contactor, and some #6 airflow restrictions will require help from an HVAC professional.
If you are in need of such a professional and don’t really have your HVAC guy to call, you can use this form here to get 4 free quotes from your local HVAC professionals.
These are vetted HVAC guys that will be more than able to help you fix the AC fan.
If we can help you in any way, just use the comment section below, describe your problem, and we will try to figure out what seems to be the problem.