How To Check And Replace Starter-Motor Brushes

How To Check And Replace Starter-Motor Brushes?

Learning how to check and replace-starter motor brushes isn’t as complicated as people think. It would help if you had a basic overview of how the starter functions and how its components are set.

For example, while fitting an endplate, you need to use coil springs to push the brushes inside the guides to easily push down the commutator. This minute yet crucial detail is not known to all. Thus, we have curated this article to make things easier for you. From teaching you the appropriate way of fitting an endplate without damaging the brushes to using a soldering iron for brush replacement, this article will teach you everything.

Components in a starter

Before we jump into how to check and replace starter-motor brushes, we need to first understand the main components that a starter is made of:

  • Electrical starter motor
  • A single pinion gear with a drive end bearing
  • Solenoid switch

How to check and replace starter-motor brushes

In both pre-engaged and inertia starters, commutators can be of two types. Dynamo usually has a cylinder-shaped commutator. Inspect the dynamo, and you will notice that the dynamo brushes’ bearings are placed on the side of a properly functioning dynamo.

Since face-type commutators have a flat disc placed on their outside, brushes bearings face against the face of the disc.

Carbon alloy and copper are commonly used to make brushes. Furthermore, they’re placed on the starter’s endplate, and you’ll usually find either two or more brushes there. Usually, starter motors must be dismantled or removed if you want to replace the brushes.

Some starter motors come with a removable band that checks at least two of the brushes without removing the entire motor. Other motors consist of a hole near the endplate that allows brush replacement with the motor in place and intact.

In addition, you can easily replace brushes without removing the commutator on inertia starters that consist of face-type commutators. In the case of pre-engaged starters, you will have to remove the solenoid.

 A service manual will tell you the exact amount of allowable brush wear. However, if you don’t have one, assume that the permissible brush wear is 8mm ahead of the brush’s lead.

Make sure to check if the brushes are easily slidable into the guides. The bruises will stick in the presence of spots. In case of spots, use a fine file to remove them.


Cleaning the commutator

 Use methylated spirit to make the commutator cleaner. Do not use engine oil, petrol, or motor oil, as it can set your car on fire with a single spark or cause a blast. In addition, do not reassemble before the methylated spirit has dried out completely. In case of discoloration, clean the commutator using a glasspaper. Furthermore, if it has been completely worn out, you will have to strip the starter motor and replace it completely.

Endplate: How to remove it

Without inspection windows, we can easily check brushes on motors. However, replacing them isn’t possible without professional help. Soldering becomes impossible due to the way the leads have been insulated.

If you want to access the brush assembly, you will first have to unscrew the bolt holding the motor. To do so, first, remove the endplate and the armature to check on the commutator. Then, remove the screws and remove the brush from the endplate’s insides.

Now, pull the coil spring and remove the bush by pulling it out from its guide. The next step is putting the brush halfway inside the guide. Secure the brush towards its side to avoid pushing the brush completely inside. This will enable the commutator to easily slide in the middle of the brushes and also help avoid any potential damage to the brushes during reassembly.

Endplate: Refitting

Use coil springs to push the brushes inside their respective guides; to easily push down the commutator to its original place. Now, join the brush and the endplate by screwing the brushes and placing a commutator in the middle of the brushes.

Then, the springs need to be released so that the commutator and the brushes can contact each other. Lastly, fix the end plate back in its place using two bolts. 

Brushes: Replacement

The first step in replacing the brushes is measuring every brush’s length. A minimum of 8 mm of brush must be present ahead of the lead. Now, move the spring upward while slipping the brush underneath. Lastly, firmly screw the lead down.

Two brushes are easily replaceable as they’re attached to the terminal post. The remaining brushes have been welded. Start by cutting the leads from the brush’s end and leaving at least 10mm. Keep filing the tags until ample metal comes into the sign. Now, use a soldering iron and cover the tags with solder. Lastly, solder the new leader in its place.

Covering Bands: Removal and checking

Placed at the motor’s side is an inspection window. A removable band covers this window in some starter motors. You can easily access the brushes by loosening this band. You will not have to completely remove the motor in such types. Ask someone to operate the starter while you take the band off. In case of sparking and arching, look for signs of wear and tear on the commutator and the brushes.

In addition, some motors use screws to attach the brushes. These screws are removable. You can detach the entire brush assembly in this type while keeping the starter intact and in place.


Removing a bolted and a spring clip endplate

You will stumble upon different kinds of endplates in different vehicles when learning how to check and replace starter-motor brushes. To remove an endplate consisting of a spring clip, you will simply have to lever the clip off using a screwdriver. Now, take off the long bolts and set the endplate free. Make sure to take the brush with the longer lead out first.

Let us now come to taking a bolted end plate out. Start by taking the armature and pinion endplate out together. Unscrew the pinion gear from the motor’s end. Then, take out the screw holding the terminal post. Lastly, unscrew the smaller bolts and take the endplate out.


Thus, knowing how to check and replace starter-motor brushes is a skill that can be developed over time. It might take a little time initially, but as you get the hang of it, you’ll gain mastery over this invaluable skill. You can also learn other car maintenance skills such as cleaning fuel pump filters, cleaning rust, fixing a car fan, or even something as simple as choosing the best tires for your vehicle. Learning car maintenance can be life-altering for avid drivers. So, what are you waiting for? Get started today!