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ML 350 Ignition Switch Replacement – Understanding The Function of The Ignition Switch System

ML 350 Ignition Switch Replacement – Understanding The Function of The Ignition Switch System

Its sleek and perfectly crafted body is what entices you, but it's carousel of modern technologies is likely what won your heart. Yes, the Mercedes ML350 was probably your dream car. That is until you ended up at a service center due to a faulty ignition switch and found out that an ML350 ignition switch replacement is going to cost you over $500. 

Auto Repairs Are EXPENSIVE


ML350 ignition switch replacement costs can vary depending on factors such as the year of the vehicle and if your Benz has additional mechanical problems related to the ignition switch failure. Here is a breakdown of the cost of an ignition switch replacement:


2004 Mercedes Benz ML350 – $164-$200

2006 Mercedes Benz ML350 – $446 – $546

2010 Mercedes Benz ML350 – $444 – $542

2014 Mercedes Benz ML 350 – $339 – $415


Ignition switch failure in the ML350 is common. When you insert your key into your Benz it powers up the starter which turns over the engine. Over time the ignition switch wears and when it fails you won’t be able to start your car. 


You can try using an alcohol wipe to clean the dust and dirt that may have accumulated in and around the ignition which can also compromise its functionality. If that doesn't improve the problem you'll have to get professional help.


What Is the Ignition Switch?

Every car is equipped with an ignition switch. Most drivers think of the ignition switch as simply the slot where you insert your key to start your car. But that’s actually called the ignition lock cylinder. 


 The ignition switch is a complex electrical component. It reads the anti-theft coding imprinted in the key before it ignites the electrical components in the car and turns over the engine.


 The ignition switch also draws power from the battery to supply the starter. Besides starting the car, the ignition switch allows you to power and turn on most of your vehicle’s accessories such as the radio and the interior lights before you even fire up the engine.


However, if you insert your key in the cylinder and nothing happens when you turn it and the dashboard doesn't illuminate, this is a sign of ignition switch failure. This can be due to a shortage in the wiring that connects the starter to the switch or a fault within the lock cylinder.


Most of the cars manufactured in the past ten years use a push to start button rather than an ignition key and switch. Instead of a traditional key, a key fob is used to transmit a signal to the car’s computer to power the engine. Several ML350 models use a push to start button. In this type of system, the ignition switch reads the anti-theft coding on the key fob before the car is started. 


The Mercedes Benz is equipped with an EIS and an ESL lock system. The Electronic Ignition System and the Electronic Steering Lock provide a layer of safety. Mercedes Bez keys are designed with a sequential code. The EIS and the ESL reads this code and allows it to crank your car’s engine if it's the right key for the vehicle. In the push to start vehicles, the key fob transmits a signal to the EIS and the ESL. 

Main Ignition Switch Positions

The ignition switch is master. It starts the engine but it also powers the vehicle’s computer, fuel, and ignition systems. This master switch has four primary positions:


Start – The start position is what starts the engine.


Run/On – When the key is in the “On” position the engine is running and all the vehicle's electrical accessories are powered.


AC -In this position, the engine isn't running but the ignition switch is drawing power from the battery to run the car’s accessories. The AC position uses very little battery power since the car isn’t running. This position is also commonly referred to as “running the car on the alternator”.


Off – In the off position the ignition switch disengages the vehicle’s electrical system. 


ML350 Ignition Switch Replacement and Anti-theft Functions

One of the most critical functions of the ML 350 ignition switch is that it also serves as an anti-theft protection device. What many people don’t realize is that the key compartment of the switch isn’t attached to the multi-contact electrical portion of the switch. Without the key, it would be difficult to start the engine.

  When you put your key inside of the ignition, the switch moves a row of pins to accommodate the key. If the pins match up correctly, the cylinder allows the switch to change the position.


On the other hand, if the pins don’t match up correctly the switch won’t be able to change the direction. Years ago car thieves would use a pry bar to remove the key cylinder from the ignition switch. Then they would use a screwdriver to manually turn the ignition switch without a key. Once automakers started implementing anti-theft systems that included a special coded computer key this made it difficult for thieves to steal cars. 


In most modern-day cars, the engine won’t turn over if the key cylinder has been removed. The ignition switch also locks the steering wheel in place. Cars that have an automatic transmission are also equipped with a shift interlock solenoid that locks the gear in Park while the steering wheel is locked. 


Common Mercedes GL350 Ignition Switch Problems

Here are the most common ignition switch problems experienced by owners of the ML350. 


Ignition Switch Doesn't Recognize The Key

When your ignition shift stops recognizing the key or the key fob this can be incredibly frustrating. Many drivers have experienced the “Key Not Detected” error message on the dashboard. Some owners have reported that the “Key Not Detected” and the “Key Detected in Vehicle” lights flashing back and forth.


If your key fob isn’t starting your car or turning the ignition it may be time to replace the battery. If the battery is too low or dead it won’t be able to send a signal to the keyless entry system. The key fob itself may be defective. 


Fortunately, you can reset your Mercedes key so that it can reconnect to your vehicle. Put the key into the ignition and quickly remove the key. Hold down the lock button on the key fob. Hold this position for ten minutes and then press the unlock button 5 times before releasing both buttons. Press the trunk and the gate button one time. Now your key fob should be synchronized with your car.


Intermittent Starting Problems

Some drivers have complained about intermittent starting problems. When the key was placed in the On position the engine wouldn’t crank, there were no lights on the cluster and none of the accessories came on. This problem persisted even after the key fob batteries were replaced. 


Key Broke Off In Ignition Switch

If you have trouble removing the key from the ignition switch and the key broke off inside you’ll need to hire a locksmith. A skilled locksmith may be able to extract the broken key and make a new key from the broken one. However, if the broken key can’t be fully removed from the ignition switch you’ll have to get a lock cylinder replacement.


Car Loses Power While Driving

One of the most common signs of an ignition switch failure in an ML350 is the vehicle suddenly losing power while driving. This occurs when the contacts inside of the ignition switch become worn. As a result, momentarily voltage loss causes the car to lose power. The engine may misfire or stall.


ML350 Ignition Switch Replacement – What Causes Ignition Switch Failure?


Just like any other mechanical component the ignition switch wears from normal use. In fact, the more you drive your vehicle the more wear you put on your vehicle’s ignition switch. In the ML350 the ignition switch rarely fails without warning. Most owners experience intermittent switch failure since this component is especially sensitive to temperature and humidity.


Here are a few of the top causes of ignition switch malfunction:


Dirty Wafers

Wafers are the unique cuts in the ignition switch that make it possible to identify the key that’s specific to that vehicle. Wafers tend to accumulate dust, dirt, and grime from daily use. When they become really worn they’ll no longer respond to key insertion. You can hire a locksmith to professionally cleaner each wafer and remove all of the particles that weigh it down.


Failed Key Insertions

Jamming the key into the ignition can make the switch tonight turn. Lubricating the ignition switch can make a big difference. Avoid using a penetrating oil that will damage the electrical components of the ignition. 


Worn Keys

Believe it or not, over time you’ll notice that your keys start to wear. As you continue to turn it over and over in the ignition the unique grooves on the key start to lose their shape and become dull. Try using your spare key in the ignition for a day to observe how your car performs. If everything works out fine you don’t need an ignition switch replacement, you need a new key!


Manufacturer Defect

In some cases, a faulty ignition switch is a result of a manufacturing defect. A defective ignition switch deviates from its original design. If your ML350 is still under warranty the manufacturer is responsible for replacing the ignition switch and making any additional repairs.


ML 350 Ignition Switch Replacement – Can I Repair A Faulty Ignition Switch Myself?

Unfortunately, an ML350 ignition switch replacement isn’t the ideal DIY project and it should be left to the professionals. This electrical component has a complex design and it works along with other important functions in your Benz. This German automaker made the ignition switch hard to remove to prevent auto theft. 


In some vehicles, the ignition switch such as the ML350 switch is located over the steering column under the trim cover. Other cars require that the ignition switch is in a specific position before it's removed or installed so that it's in alignment. Some of the newer ML350 models use sophisticated smart key anti-theft systems that have to be reprogrammed after a new ignition switch is installed. 


Of course, whenever you have any work done on your Mercedes Benz you should seek out a certified Mercedes technician who has experience working on these foreign vehicles. 


Can I Jump Start A Car With A Bad Ignition Switch?

Once the ignition switch completely fails you won’t be able to start your car with the keys. When you need to get your car running and you can’t afford to pay a tow truck you can always bypass the ignition system. The easiest way to get your car started with a bad ignition switch requires a battery jump starter.


Pop open your hood, locate the battery and the ignition coil. Connect your portable jump starter to the positive battery terminal and the positive side of the coil. Next, locate the starter solenoid and hook it up to the positive side of the battery terminal.


 Unplug the ignition switch wiring from the starter solenoid. If you can short the starter solenoid’s positive terminal to the stud where the ignition switch was attached too. This should get your car started. When all else fails you can always hotwire your car. 


Can I Drive My Car With A Bad Ignition Switch?

When you’re dealing with ignition switch issues driving your car in its current condition can be dangerous. The engine can end up stalling when you are in traffic or the car can completely lose power while in motion. If you decide to bypass the ignition switch by jump starting the battery and starter you should take your vehicle to be serviced.


The Bottom Line

A bad ignition switch causes several mechanical malfunctions that negatively affect the performance of the ML350. Ignition switch failure cases can vary and every motorist experiences different symptoms related to this problem. Some have been subjected to several operational issues while others may experience an unexplainable electrical mishap that can be attributed to ignition switch failure. 


The ignition switch supplies power from the battery which is why an ML350 ignition switch replacement is imperative. Taking care of this problem should be a priority. Once you have your car’s ignition switch repaired you will have peace of mind knowing that your car is more reliable and you don’t have to worry about getting stranded.