How many brushes does a starter have

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For a better experience, please enable JavaScript in your browser before proceeding. How many brushes in a starter? Thread starter dgadee Start date 12 Oct Joined 13 Oct Messages 2, On advice of a diesel mechanic friend, rather than have what seems to be a 'lazy starter' tested and rebuilt, I bought a replacement.

I decided to take the original apart to see whether it would be worth keeping as a spare. I expected to see four brushes inside, but there are only three north, south, east. No sign that it wasn't built that way engine is from mid 90s. Am I wrong and three brushes is ok?

Phoenix of Hamble Active member. These refer to conditions when the motor is in rotation. They also involve the commutator since the two components maintain contact throughout. The main ones include:. Surface Condition- When the motor is spinning, a film of copper and humidity forms on the commutator surface. Carbon or graphite dust from the brushes also settles on the commutator. This film helps to reduce friction and heat, protecting the brushes from excessive wear and damage.

But the film must be within limits for the described conditions. If too thick, current transmission drops and friction increases. The same case happens if the film is too thin. To produce the ideal film, the commutator surface must not be too smooth or too rough. The mica undercuts on the commutator must also be right. More importantly, the brush grade should be the right material. Low quality starter brushes cannot achieve a quality surface film They are often the reason for the rapid wear, chipping, and other forms of damage.

That can cause damage or even improper brush operation. With the right design, though, starter motor brushes can be made to withstand vibrations. Fixing broken motor parts also helps to reduce vibrations and damage. Brush pressure- As we saw earlier, the brushes of a starter motor are always under spring tension.

The pressure must not exceed certain limits or reduce too much. It should also be uniform across all brushes to ensure proper seating of the brushes on the commutator. For that, the brush design and size should be right. The springs should also be intact at all times. Coefficient Friction- The friction caused by the starter brushes should be low enough for different conditions such as speed, commutator surface, and load. This is to avoid overheating and premature damage to both the commutator and brushes.

Coefficient friction is usually determined by the brush quality, which is why you should always go for the right material and brush grade. Brush holder height and clearance- Both must be ideal to allow proper brush operation. Insufficient clearance and wrong height can lead to problems such as the starter brush sticking in the holder or brush noise when the motor is spinning.

Physical requirements are environmental conditions that affect the operational tendencies of starter brushes. They are mostly caused by external materials. The main ones are:. Corrosive gases- Corrosive vapors can cause damage to the commutator surface, and therefore, the brushes. Examples include sulfur dioxide , ammonia , and other gases. The vapors can affect the essential film that develops on the commutator when the motor is in operation.

This leads to excessive friction and overheating, among other problems. Liquids- These cause brush contamination and reduce performance. They are often responsible for problems such as sticking starter brushes and commutator damage.

Main contaminants include oil from leaking bearings and water from condensed air. Keeping the liquids off the brush and commutator assembly would prolong brush life. Humidity — It forms part of the film that occurs between the commutator and brush to reduce friction and overheating. In its absence, the film mostly comprises abrasive metal oxides. The situation results in rapid brush wear and reduced lifespan.

Ensuring proper electrical conductivity and mica undercutting on the commutator can help maintain the film. Dust- A buildup of dust can harm car starter brushes. Dust increases the wear rate and can even cause grooves to form on the brush surface. Conductive dust can also cause electrical flashover and surface wear. The ideal conditions also help to extend the lifespan of the brushes, reducing maintenance costs. Before concluding this guide, here are answers to questions you might stil have about the components.

Automotive starter brushes are often little known, partly because they operate hidden inside the motor. We answered the most popular questions about them. It depends on many factors such as the type and grade of material used to make them, their quality, design, and how frequently a car is started.

Also, the load and operating conditions. Starter brushes tend to wear quickly than many other components, though. You should expect about to hours on average for metal graphite brushes. They are many. Generally, the signs of bad starter brushes include reduced power or torque, excessive sparking or arcing, and total motor failure.

Worn starter brushes cannot conduct current properly, while broken ones may not even contact the commutator. Many factors can result in the failure of these components. Common reasons include constant heavy sparking, frictional wear, impurities, chipped surfaces or broken brushes, and burned wires. Wear and breakage may result from excessive mica or surface spots, stripped surface film, unequal brush pressure, and electrical problems.

Fixing starter brushes usually involves changing them. You can easily do that using a repair kit. The pinion, endplate and armature can then be pulled straight out of the motor housing as a single assembly. The brushes on this type of starter often have convex faces bearing against the commutator. Making sure the new brushes are fitted the right way round before you reassemble the starter. The Video Course teaches you everything about modern cars.

Pull out the brush assembly. Unscrew and pull out the two long bolts to release the endplate; pull out the armature. Undo two screws to release the brush assembly. The leads are insulated in a way which makes soldering on a new brush impossible. Take off the endplate and pull out the armature to check the commutator.

Release the brush assembly from inside the endplate by removing two screws. Measure the length of each brush from the face to the near end of the lead. There must be at least 8mm of brush beyond the lead. Not all dealers stock replacements; so be sure to have a new clip ready if you remove it. Two of the brushes come already fixed to a terminal post, so are easily replaced.

Solder the new leads in place, ensuring that the joints are solid, neat and flat. Lever off the spring clip with a screwdriver, taking care not to damage the end of the shaft. Remove the two long bolts to release the endplate.

Note which of the brushes has the longer lead before you take them out. Take care not to damage the armature or commutator faces as you withdraw it. At the other end, unscrew the nut that holds the terminal post. Remove the four smaller bolts to free the endplate. With the endplate removed, note which brush has the longer lead before you take them out.

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