An impact wrench is a high torque power tool that uses for lug nuts operations. When an impact wrench is used for a long time, its performance can be reduced due to many reasons. Mostly torque is reduced when an impact wrench is used continuously due to the below reasons.
An impact wrench power is lost due to brush wearing, winding burning, low battery capacity, broken trigger, worn bearings and rarely, magnets can be crashed due to damages. More than this, lack of lubricants, overheating, back EMF also will be the reasons for impact wrench lose power.
Let’s see how these are affected by the impact wrench performance. Here I have added all in detailed facts. I included how to fix it quickly and avoid it. So take a look until you have the solid solution below.
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Worn Brushes

When you use a brushed impact wrench, you can see there is a carbon brush that will touch the commutator. The brush is used to supply the current to the winding (wiring loop). Each and every rotation brush is in touch with the commutator. When the brush touches, it can be worn due to friction. There is spacing in the commutator. When the brush is moving on it, it can be scratching.
When the tool is used for a long time, its brush is worn, and the electric supply can be weak. When the electric supply is weak, it affects the motor rotation directly. So you had better change the brushes when they reach 1/4 of the original length. Sometimes worn particles can be attached to the inner parts, and it can short the commutator panels.
Use the tool in low temperatures. It will help to minimize the wearing due to friction.
Low Battery Capacity
When a battery is used for a long period, its capacity can be decreased. Because battery current is a result of a chemical process. When the same process is happening for a long period, its efficiency can be decreased. If we see the battery has fully charged but it may not. When we use that kind of battery, it can discharge quickly.
If this is happening continuously, replace the battery. Before you use the battery every time, make sure it is fully charged. Follow the steps on how a battery can last long with its maximum efficiency.
Read More About – 09 Most Drill Battery Problems and Solutions
Winding Burning
When we consider the brushed motors, we can see there is a wire wrapped around the armature. Normally when the windings are increased, its power and smoothness also increased. When the winding is damaged due to any reason or burning it, its power can be reduced from the total power.
Although a winding plane has burned, the motor can be worked. But it will not produce the maximum torque and power that the motor had. Its efficiency can be reduced due to this. You can observe only the torque has reduced when you use it.
You have to use an experienced electrician to check the windings. Changing the brushes will not solve this.
Sometimes dust can scratch the winding, and due to electricity, it can be short and burn. So make sure to lubricate the tool as much as possible and not to use it in the dusting area.
Trigger Damage
The trigger is used as a power switch of the impact wrench. When the trigger is pressed, it provides electricity and power is generated by the motor. Mostly RPM depends on the trigger pressing. If we press less, there is low RPM, and if we press completely, high RPM can be seen. So now you can realize if there is a problem with the trigger, its RPM can definitely be changed.
If the trigger inside is clogged with dust or damaged wire and the current is leaking, its performance will not be seen. To test the trigger with proper RPM before you use it. When you see this while you are working, you can see there is power lost. Service and maintain the trigger correctly.
Worn out Bearings
This is mostly happening in brushless motors. The bearing is used to fix the rotor with housing. So bearing supports to complete the rotation of the rotor. If there is a problem in the bearing, it can directly affect the impact wrench spinning mechanism. So if you use a brushless motor, you should pay attention to this matter. That is the most problematic part of the brushless impact wrench.
You can replace the bearing if there is a problem. But identify that early to reduce the damages.
Read More About – Can you Burn Out a Brushless Drill?
Magnet Crashing
This is a really rare situation. If the tool is dropped from the high, it can break the inner magnets. When the magnets are breaking its magnetic field can be weird. So we can’t have the expected power from the tool.
If you use the brushless impact driver, this can be seen. Because most magnets are included in the rotor which is outside the stator.
If the torque is reduced, remove the part by part to find the problem.
Power Supply Problems
Electric impact wrenches are of two types. Cordless and corded are them. Both are based on the power supply to the impact wrench. Normally corded impact wrenches are powered with the permanent power cord. If there is any damage to the power cord, its performance can be reduced. So you had better check the power cord for a better power supply without any problem.
If you use the cordless impact wrench, its battery and tool can be overheated due to high torque usage. So performance can be reduced due to this. Do not use the impact wrench in the high torque requirement area.
When you fix the battery, it can be loose fixing. So its power will not receive to the motor. Therefore you can see there is low performance. Make sure the battery is fixed with the tool, and there are no internal particles to clog the connections.