How To Tell If A Brushless Motor Is Bad

How To Tell If A Brushless Motor Is Bad?: A Quick Guide

Do you have a brushless motor you’re not satisfied with? Maybe something’s wrong with it. Often people don’t understand when a brushless motor has gone bad. But not anymore, we’re here to help you!

So, how to tell if a brushless motor is bad?

Well, You can tell if your brushless motor has gone bad by observing some signs. The motor will overheat, and make loud noises. The motor will vibrate extremely while running. If you look inside, you’ll notice burnt windings and loose magnets. All these signs are indicators of bad motor.

This was just a short briefing. You have to understand a bad brush motor’s sign to the depth. We have provided detailed information on this. 

To find out more, you have to keep reading!

How to Tell If Your Brushless Motor is Bad?

You can easily tell if your brushless motor is bad by looking for signs like high power drain, overheating, etc. 

It is pretty easy to tell if your brushless motor is not functioning as it should. These are the signs you should look out for- 

Signs of a Bad RC Brushless Motor

A bad motor usually leaves some noticeable signs that can indicate its damaged condition. There are 4 telltale signs that point toward a bad RC Brushless motor.

  • A high power drain
  • Overheating
  • A burning smell
  • No power

The table explains the reasons behind the signs. 

SymptomsReason
High Power DrainBad Tuning, Faulty Motor
Overheating and Burning SmellExcessive Voltage
No PowerBad ESC, Dead Motor

However, the signs will not be obvious all the time. Throughout my time as a hobbyist, I have seen many bad motors. There were many whose signs were too subtle for many to notice before it was too late.  

In that case, there are 3 ways to check your brushless motor. I’ll discuss them in the next segment. 

3 Ways To Check If The Brushless Motor Is Bad

If you’ve been wondering how to test a brushless RC motor, you’ve come to the right place. I’ll teach you the three surefire ways I use to check if a brushless RC motor is bad. 

A diagram of a brushless motor
Source: Tyto Robotics

Let’s start discussing the first method. It’s not my favorite one.

Method 1: Check the Brushless Motor Parts Individually

The first method is the most obvious and also the most tedious one. That’s because you need to check every component of the motor one by one. Here are the steps- 

Step 1: Check the Motor Fan: First things first, a Motor fan is vital for cooling your motor. If there are any issues in the motor fan, it causes overheating and ultimately, motor failure. So, a faulty motor fan is one of the reasons behind a bad motor. 

Step 2: Check the RC Bearings: Secondly, the bearings of your brushless motor wear down with time. All you need to do is check for rust, or signs of corrosion in your bearing. 

Worn-out bearings cause disruptions in the motor spin that will cause the motor to stutter. 

Step 3: Check the Windings: Finally, check if your winding is stuck like glue with the magnet. If it is, then you have a burned-out motor. The brushless motor will not spin at all in this case.

If you’re like me and you want the easy way out, the next methods are for you. 

Method 2: Dry Test the Brushless Motor 

This is the safest method to test your brushless motor. Because you won’t have to risk your ESC for the test. However, You’re going to need some tools in the first place to test the brushless motor. They are- 

  • A tester and a multimeter will do the job just fine. You’ll need to set it to test for continuity for properly testing each phase of the motor. 
  • A holder to hold the motor in place. 
  • An alligator clip for the wires. 
  • An RC car to start the motor up. 

Here are the steps you’ll need to take to test the brushless motor without an ESC- 

Step 1: Check the Voltage

  • Label each wire. I’ll label it with A, B, and C in my case. 
  • Check the voltage of each wire from the motor individually with the tester. To do that, first, connect the voltmeter to the AC range.
  • Then connect any two wires to terminals 2 and 1. Try all the combinations of wires.
  • Lastly, compare the voltage at both full spinning load and no load with the specs and see if it checks out. Also, check if the motor winding is properly grounded with the stator. 


Step 2: Spin the Motor Shaft

  • Now spin the motor shaft with the wheels of the RC car and take the reading to get the KV rating. 
  • Be sure to test the motor at full throttle. 

Now, if the KV rating matches the specs, then the motor is A-okay. If it is not, then you have a bad motor in your hands.

This youtube video explains further how to properly dry test your brushless motor- 


Here comes the method that bears some risk as I’ve mentioned before- 

Method 3: With ESC

Testing the brushless motor with ESC and without ESC is the same in principle. The RC car that I used in the method earlier, is replaced by the ESC in this case. 

However, there’s a catch. You can damage your ESC if the brushless motor is faulty. 

First set the ESC to drill mode, so that it will spin the motor. Then set it to variable speed to test the motor at different speeds. That’s it! you’ll be able to test the motor just like the dry test method. 

I talked about the problems, and I also properly explained the testing method of a brushless RC motor. It’s now finally time to talk about the solutions.

RC Brushless Motor Problems: A Quick Glance

Almost all modern RCs that come out these days have brushless motors. And they can also be exposed to a lot of physical problems. 

Here’s a quick glance for those who don’t have much time on their hands- 

ProblemSolution
RC brushless motor faster in reverseRecalibrate the throttle, Check the ESC-Motor connection
RC brushless motor overheatingCheck the tuning and placement of the motor, Replace the motor if needed
RC brushless motor stuttersCheck the ESC, Replace the ESC if needed
RC brushless motor won’t spinReplace the wiring, Check the ESC
RC brushless motor stops at full throttleReplace with a higher capacity battery

If you’re still here, I’ve got some good news for you. I’ve added a little bonus for you at the end of the troubleshooting. With that out of the way, let’s dig a little deeper into the problems. 

RC Brushless Motor Faster In Reverse

If your brushless motor runs faster in reverse, the problem is not in the motor itself. A messed-up throttle calibration causes the motor to be faster in one direction. The only other reason is messing up the motor-ESC connection. 

Brushless motors
Source: RCGeeks

I have explained the reasons in greater detail right below for you guys. 

  • Throttle Calibration: The first thing you do while setting your RC up is calibrate your throttle. Setting the throttling range is part of the process. You usually calibrate the throttle while calibrating the ESC.

    So, if your motor is faster in reverse, chances are you’ve messed up in the calibration.  
  • Motor-ESC Connection: There are three wires connecting the motor to ESC. Messing up the order of those wires leads to the motor running faster in reverse. 

These two are the only reasons why your motor spins faster in reverse. Worry not, the article has the right solution for you too. 

RC Brushless Motor Overheating

Overheating is one of the more common problems I have faced with RC brushless motors. A lack of ventilation and bad tuning are often the culprits that overheat a brushless motor.
However, if both of these aren’t the reason, then you might be dealing with a bad brushless motor. 

  • Lack of ventilation: Brushless motors heat up easily because of the power they put out. Lack of air to push the heat out will lead to the motor overheating. Ample air is vital for these RC motors. 
  • Bad tuning: Tuning a brushless motor improperly leads it to work inefficiently which results in a heat buildup. This kind of overheating is common in RCs. 
  • Bad brushless motor: Bad brushless motors generally have worse efficiency than good ones. Pair that up with a high power draw, that’s a hotpot too hot for the motor. 

That concludes why your brushless motor is overheating, I’ll now get to the stuttering. 

RC Brushless Motor Stutters

A stuttering motor is especially annoying, it took the fun out of many sessions for me. However, the motor in this case is usually innocent. A problematic ESC causes the motor to stutter. 

A Brushless ESC
Source: HobbyKing

Here’s a breakdown of the reasons why your brushless motor stutters- 

  • Bad ESC: Electronic Speed Control like its name suggests controls the speed by which a brushless motor spins.  If there’s a problem in the ESC, it will cause your motor to stutter. That’s primarily due to the improper regulation of speed. 
  • Bad motor: The motor is usually innocent in this case, but that doesn’t mean it always is. Worn-out bearings can cause a brushless motor to stutter. 

 That wraps up why your motor is stuttering. But what if it doesn’t spin at all?

RC Brushless Motor Won’t Spin

If your RC brushless motor is not spinning at all, the first one I’d suspect is the motor itself. Furthermore, the ESC is also a possible suspect in this scenario. The reasons are- 

  • Frayed motor wiring: If your motor wires are frayed, then they will naturally stop spinning. Checking it is a hassle though since you’d need to take out the motor to check it. 
  • Bad/ Faulty ESC: If your ESC is bad or faulty, then you won’t be able to start your motor. At least not without taking extra measures. Hence it won’t spin. 

That covers all things that cause ESC motors to stop spinning at all. 

RC Brushless Motor Stops At Full Throttle

If the motor runs fine till it’s at full throttle, the problem is not in the motor itself. Stopping at full throttle points to a lack of power. The battery likely cannot support the brushless motor in this case.

Here’s my take on the rest of the reasons including this one- 

  • Low-capacity Battery: Let’s assume the brushless motor draws more power than what the battery can supply it with. The motor, in this scenario, will stop itself at full throttle. 
  • Overheating: Brushless motors tend to heat up exponentially more at full throttle. That leads to the motor overheating and stopping itself. Normally, this shouldn’t happen. A bad motor may be at play here. 

Why Is My Brushless Motor Not Working?

There are a plethora of reasons why a brushless motor stops working in an RC. I have narrowed them down to make it easy for you.
A bad brushless motor, bad plugs, loose connections, bad battery, frayed wiring, etc can be blamed for your non-functioning brushless motor. 

In such a case, try fixing the motor connections first. If that doesn’t work, replace the motor with a new, durable one.

These are the problems I faced the most in my experience with brushless RC motors. On the topic of bad motors, I’ll further explain how to tell if it is actually bad. 

Is It Possible to Fix a Brushless Motor?

It is possible to fix a brushless motor given it isn’t a faulty one. However, it is better to get a new brushless motor instead of fixing the bad motor.

Brushless Motor Dissected
Source: Hackaday

Don’t worry! I know how to fix a brushless motor too. So let’s get to the troubleshooting, shall we?

  • Replace the brushless motor: Even if fixing a brushless motor is possible, it is not very long-lasting. Every time I did fix a bad motor, it started showing issues again before long.

    If you did decide to get a new brushless motor, the Readytosky 2212 is a great choice for your RC quadcopter. As for cars, Hobby Fans F540 is my personal favorite.

    Or if you want a nitro engine instead, I got you covered on the best nitro engine.
  • Buy a High Capacity Battery: Let’s assume your brushless motor is not getting any power or is stopping at full throttle. That usually means a weak battery.  Either that or your connection might be loose.

    I think the Zee 7.4V Lipo battery is a great choice. I myself use this on most of my RC trucks.
  • Replace the ESC: If your motor stutters, or won’t spin, the ESC is usually the main offender. You could either take it to a shop for repairs or buy a new one.

    It could also be a weak connection. In that case, here’s how you can properly connect your ESC to the brushless motor.

    Otherwise, You should only buy a brushless ESC for a brushless motor like the UBEC 30A one. Do make sure to match it with your motor’s amperage first. 
  • Tune the motor: Not properly tuning the motor is a mistake I’ve made a lot of times. Improperly tuning it can overheat it, so I’d suggest you re-tune the motor and check if it’s still overheating.

    If it is, make sure there’s ample airflow in the placement of the motor. Otherwise, you will have to replace the motor. 

These are the possible solutions to a bad brushless motor. They’ll fix almost any issues if it’s with brushless motors.

That’s about it, folks! I’ll answer some of the frequently asked questions before wrapping up.

FAQs

Are Brushless Motors Better than Brushed Motors?

Brushless motors are indeed better than brushed motors. Brushless motors are more efficient and outperform brushed ones in all scenarios. 

How Long Do Brushless Motors Last?

Brushless motors last tens of thousands of hours on average. That’s more than 2 years in terms of your calendar. 

Are Brushless Motors Waterproof?

Brushless motors are not always waterproof. It depends on the model you’re getting. Some of the models are waterproof, while others aren’t. 

Final Words

That’s all about how to tell if a brushless motor is bad! I hope I was able to help you out. Is your problem still persisting despite the solutions?

Let me know in the comments below and I’ll get back to you as fast as I can. Till then!

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