Today, we’re looking at another essential component of your car—the starter motor. We’ll explain what it does and how it works, how to spot when it’s on its way out and your options to repair or replace it. We’ll also answer the question at the top of everyone’s list: how much does it cost to fix a starter motor?

Okay, let’s start with the basics.

What is a starter motor?

It’s exactly what it sounds like. It’s an electric motor whose job it is to start your car’s engine.

As motors go, this one has to be pretty heavy-duty, as it needs a lot of torque to turn your engine. Your engine has to turn at high enough speeds to suck the fuel and air into the cylinders, as well as compressing them, ready for ignition.

How does a start motor work?

When you feed electric current into the coiled wires of your starter motor’s armature, it reacts to magnetic plates located around the body housing—and spins. It’s then down to some gears and a flywheel to transfer this movement to your engine.

As simple as that sounds, there are a lot of components built into the process. All of these components are susceptible to wear over time. Given how hard a starter motor works, it’s sensible to consider that it could fail at some point over the car’s lifetime.

There are coils, an armature, and brushes that deliver the electric current. Your motor also needs a switch to connect the motor to the engine. This switch is the solenoid. The solenoid is one of the key elements in the process, and sadly, one that’s susceptible to failure over time.

It takes a lot of power to spin the motor and turn your engine. This is why a lot of starting issues are down to the battery or the starter motor. Both motor and battery can have an impact on the life of the other.

Starter motor components

For a relatively simple operation, there are plenty of working parts in this system.

  • Heavy-duty connection wires from your battery – they need to be fairly thick to carry the amount of current from the battery required to turn the motor
  • Electric coils
  • Magnetic plates
  • Contact brushes
  • Armature
  • Bushes
  • Pinions
  • Solenoid

When a starter motor fails, it’s often down to the same few things. The brushes have worn out, the coil windings on the armature have failed, or the solenoid has seized.

You’d like to think that if you could diagnose which element is the guilty party, it would be cheaper to isolate it and replace it. Stripping a starter motor and rebuilding it can be both a time-consuming and pricey process—especially considering that locating specific individual components can be time consuming by itself. That’s why, in the best interests of everyone’s time and resources, it’s almost always better to replace the complete unit.

How do you know if there’s something wrong with your starter motor?

The biggest telltale sign is that your car won’t start! It’s not always the fault of the starter motor, it could just as easily be your battery, but it’s a strong possibility.

How to recognise starter motor problems

  • Nothing happens when you turn the ignition key/press the start button
  • You hear a single click from the starter motor
    The single click is usually the solenoid firing—but only once. It could be down to a battery problem, or it could be a seized or damaged starter motor.
  • There’s rapid clicking from the starter motor
    Rapid clicking suggests that while the battery has enough power to keep firing the solenoid, there isn’t enough to physically turn the motor. In such an instance, check the battery for charge.
  • Smoke appears from under the bonnet
  • The starter motor is soaked in oil
  • There are grinding noises when trying to start your car

How much does it cost to replace a starter motor?

How much to replace a starter motor depends on the make and model of your car and where you have the work carried out.

There’s always a decision to be made whether to repair a starter motor or have it replaced. Given the cost of parts compared to the cost of labour, generally, it works out more economical just to replace the complete unit. We’d advise you leave that decision to your mechanic.