2004 Mercedes-Benz SL500 Starter Replacement Cost

The starter solenoid receives power from the battery at all times. When you turn the ignition to the start position, it sends an electrical charge to the solenoid, and allows battery power to move from the solenoid to the starter motor. This causes the starter motor to turn the engine's flywheel, forcing the crankshaft to turn until the engine begins running on its own.

Starter motor failure produces one common symptom across all makes and models: When you turn the key, the starter solenoid will click, but the engine will not rotate. You also might hear a whirring, or fast spinning noise when the key is turned. In this case, the starter solenoid and starter should be inspected for failure.

Vehicles with automatic transmissions won't start if there's a problem with the starter. If your car has a manual transmission, it is possible to start the car by turning the key to the "On" position, pressing in the clutch, pushing the car until it gets up to about 10 mph, and then releasing the clutch. However, this method is difficult and can be dangerous, so you should get the starter replaced right away.

Most vehicles will have a starter fail at some point. Failure rates are low for the first 75,000 miles or so, but after that, the rate of failure increases dramatically, with the majority occurring around the 125,000-mile mark. Vehicles that start and stop frequently, such as newer cars with automatic engine start-stop functionality, are at a higher risk of premature failure. 

A mechanic will connect a vehicle that won't start to a starting and charging system test machine. The machine will display results and indicate the possibility of starter failure, but it may also require the technician to do visual inspections while testing is in progress. If the starter is found to be at fault, it will be removed, bench tested and replaced. 

The battery is disconnected to prevent electrical shock or damage to electronic components, and then the starter motor is disconnected from all its connectors. It's then removed, and the new one is installed. During installation, the electrical connections must be placed on the correct terminals, also known as “posts”, and the replacement starter should have the same number of posts as the original.

We recommend using a high-quality replacement starter motor and solenoid. Replacement with an OEM starter can reduce the risk of another replacement later on.

If your car won't start, it's not always the starter's fault, of course. If the starter won't turn the engine, it could be caused by a faulty ignition switch, blown fuse or bad starter solenoid. The starting and charging system will need complete diagnosis. When installing a new starter, its electrical connectors can accidentally be installed in the wrong position. This will cause further problems once the battery is reconnected. Many starters for the same car brand will fit many of its models mechanically, but the solenoid may not be the same design. The appropriate part number must be used when choosing the new starter, or the starter motor may fail to function properly.

On most models, replacing a starter is a great DIY project. Still, there is a risk of electrical shock and other electrical component failure if the battery is not disconnected first. On many older vehicles, the starter motor is installed using shims to make sure everything is aligned correctly. If this is the case with your car, have a professional mechanic do the repair — any mistakes could cause damage to the engine's flywheel or other parts.