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If you have owned a quadcopter for long you likely have wondered whether one of the motors has started to go bad if you experience any issues while flying or a sudden change in the amount of power that it has. Of course changes like this can happen for many other reasons as well so just because your power has decreased doesn’t always mean the motor is bad.
The best way to know if your quadcopter motor is bad is to use a multimeter and measure each phase for resistance. They should all be the same if the motor is fine. You can also spin the propellor by hand to see if it turns properly or not.
If the bearings have gone bad then that propeller won’t spin properly which means that motor will need to be replaced.
Honestly when things go wrong on a drone it is rarely because of the motors if they are brushless since brushless motors will typically run for years without any problem. If you are facing an issue it will normally be from the wiring, ESC, battery, etc. rather than actually needing a motor to be replaced.
Another common thing that you can do is smell the motor after running it for a while. If it smells like something is burning then that is a sign that the motor is going bad as well. You can also look at the motor and if the windings look black or dirty then it is likely an issue.
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How to test a quadcopter with a multimeter
Since this is the most common way to test a quadcopter motor to see if it is any good we wanted to go into a little more detail about this method of testing your quadcopter motor.
To do this method you will want to turn your multimeter to the continuity and sound setting. You will then hold the two leads on each other and you should hear a sound. Once you do that then put each end of the multimeter on two different wires from the motor and see if you get a sound.
If you get a sound then your motor is good to go. If there is no sound then that means your motor is bad.
However you should be careful as it’s possible for the wire to not be making good contact with one of the leads on the multimeter so be sure that the leads are touching both wires at the same time before you throw the motor away.
This is by far the simplest way to check if your quadcopter motor is bad and also the most simple way.
How to know if the quadcopter motor is bad or the ESC?
Often when people have a drone motor that isn’t spinning it is quite difficult to tell if it’s the motor or ESC that is causing the issue. You can of course use the multimeter test mentioned above to try and determine if the motor is good but the test really only tells if the wiring is passing the current through the motor properly and it really isn’t an end all answer to whether it’s the motor or ESC that is causing the problems with your quadcopter.
The best and only truly accurate way to know if the motor or ESC is bad is to swap them out with a brand new part and see if that fixes the issue. If you swap out the motor with a brand new one and the problem persists than the ESC is bad and Vice versa.
Of course one huge downside to this method of testing is that it requires you to take off the old motor and attach the new one and the same for the ESC but really this is the only surefire way to tell 100% which one is causing the issue.
Can a bad ESC burn up a motor?
If you have recently replaced the motor on your drone/quadcopter and then the motor again died soon after being replaced you might be wondering whether the ESC is to blame or if the motor was simply faulty.
Although it is possible for a new motor to be faulty it’s also possible for an ESC to damage a brand new motor.
If your quadcopter is having engine problems it is normally best to replace both the ESC and the motor at the same time to prevent a bad ESC from destroying a good motor or for a bad motor to destroy a good ESC. Both bad motors and bad ESCs can destroy the other one so replacing both at the same time prevents this from happening.
Now I know replacing a part that might not be bad might seem insane and a waste of money but it’s better than burning through multiple motors because of a bad ESC or burning through multiple ESCs because of a bad motor.
Neither the motor or ESC on quadcopters are very expensive so if you have to replace one it’s always the safest thing to simply replace them both.
Can a burned out motor be repaired?
If you had a bad ESC and didn’t realize it until you burned up a brand new motor or your ESC went bad and burned up your motor soon after repacking it you may be wondering if there is a way to repair your quadcopter’s motor.
On most small drone motors it is really not worth repairing them as the cost to do so is typically more than what it would cost to replace it. On larger motors you can rewind them to save some money but on drone engines it just isn’t worth it.
This is why we always recommend that you replace the ESC and the motor at the same time if one of them has gone bad. It prevents you from spending money unnecessarily if one or the other goes bad and burns up the other part.
Can you burn out a brushless motor?
Often many people think that since brushless motors don’t have brushes then they can’t get burned out but is this true?
Brushless motors that are well taken care of will last virtually forever so technically they won’t “burn out, however it is easy for solders to come loose, bearings to go bad, or even to have a winding path failure.
Although all of these things will cause a brushless motor to stop working they are also things that can be repaired quite quickly and easily if you have any experience with brushless motors at all.
What it really comes down to is whether the motor is worth repairing or not. The super cheap brushless motors will continue to perform worse and worse over time as the heat from the motor causes the magnets to not work as efficiently. More expensive brushless motors will typically last for years so if you have one go bad it is likely one of the easy fixes mentioned above that can be done in a few minutes.
Conclusion
I hope this article has been helpful in determining if your quadcopter motor is bad or if it is something else that has caused the issue.
Ultimately the easiest way to know is to test a new motor with the current ESC or test a new ESC with the old motor. You can also just swap out both the ESC and motor with new ones and if that fixes the issue get back to having fun!