Reasons Why Mercedes Won’t Start But Lights Turn On

Tim Miller

Do you know the reasons why Mercedes won’t start, but lights turn on? You might be thinking something is seriously wrong, but it is a common problem.

No car breaks down if everything is working correctly. In case the car doesn’t start, but the lights are working just fine, it can be one of the many problems. One of the reasons is a dead battery. However, there can be other reasons, too. So, when this happens, you should perform a few troubleshooting methods.

Let’s take a look at the probable reasons and how you can troubleshoot them.

Reasons Why Mercedes Won’t Start But Lights Turn On

Probable reasons that Mercedes won’t start but lights turn on
Three reasons why your Mercedes won’t start but lights turn on

A Dead Battery

One of the primary reasons is because it has a dying or a dead battery. Simply because a few HTE parts are not working, it might run low charge. The charge is too low for the car to start over, but the light will come on.

The car parts, like radios, headlights, and other electronic parts, need little power. So, it runs on low and even on a dead battery. However, the engine might need 300 amps to start. This is too high for a battery that is running on a low charge. So, the car light continues working, but it doesn’t turn over.

Use a hydrometer for testing the battery’s charge. If it tests low, you will have to replace the battery. You can also perform a load test on the battery.

In circumstances when the battery has a low charge, you can get it charged from another battery. This way, you can solve the issue of the car not turning over. You can repair or replace the battery. But it largely depends on your car’s worth and how much you are ready to spend.

For some people, replacing the battery of the Mercedes might not be worth the cost.

However, if the Mercedes can’t start after replacing the battery, it might be because the car has a blown fuse.  To troubleshoot this, you will have to proceed to the next point.

Blown Fuse

Fortunately, you can easily tell if the car has a blown fuse. Detecting a blown fuse is the first step you need to take to figure out the fault in Mercedes’s system that keeps the engine from starting.

The signs that you have a blown fuse are that the accessories in the car will lose power. Its fuse will appear disjoint, or the circuit will start to overload. This can make the engine not turn over even when the lights are turning on.

How to detect a blown fuse?

Check the car’s manual to find out the fuse box’s location. After that, you will have to check if there is damage to the wire. In case the metal wire is disconnected or damaged, a blown fuse might be keeping the power from reaching out to the starter relay.

Perform a check, and it will help you to understand if the fuse is in good shape. If there is a fuse problem, the Mercedes’ ignition switch might not be working correctly. However, opposite to popular belief, ignition is not the mechanical hardware put into the key when you look to start the car. It can be the electrical switch inside which the key touches when you insert the mechanical part in the ignition.

In some instances, the ignition switch might only give the electrical components power and not to the engine starter.

Another thing that indicates a failing ignition switch is if you see problems with turning on the car accessories. When you put the key and turn it on, the accessories will not power on. This means that there are fuse or ignition issues.

Diagnosing an ignition switch can be a little complex. However, the best way to do it is to check if the dashboard light or ignition panel doesn’t turn on to remove the ignition key. This indicates the issue is with the ignition switch.

Starter Problem

Another reason is that the starter is not working correctly. It is the electric motor that cranks up the engine to turn on the car. The starter system consists of the solenoid and the motor that takes the battery power and gives it to the flywheel and the motor.

So, to start the car, you will require high current. It lets the engine have enough power to start the car properly. Whenever the car doesn’t start and the battery has enough charge, the starter motor is the primary culprit behind the problem. 

One of primary reasons that Mercedes won’t start but lights turn on is starter problem. There are some signs that show common those starting issues
Some signs that warn you about starter problem

Signs that show common starting issues

  • The starter can doesn’t crank, but the car doesn’t start. It is basically because of battery failure. This happens because something has been left on, causing it to drain its battery. The problem can also be caused by a damaged or dead battery.
  • You are wiggling the key for turning it on. It shows that you have a bad ignition switch and the solenoid isn’t going to be activated. The car might start when it is in a neutral mode, but not when you park it.
  • The last sign is the lights going dim when you start the car. In this case, you have to check to find out if the problem is the starter control circuit. This might be because of a starter relay, neutral safety switch, and ignition switch.

Any of the above reasons can damage the starter and prevent the car from turning over. 

In case you find that there is some issue with the starter, you might have to replace it. You can take the help of a mechanic if you want. To avoid mistakes, it is better to get in touch with one.


So, we have covered all the significant reasons why Mercedes won’t start, but lights turn on. In case all these are too difficult for you to understand and you find yourself in a fix, you can take the help of a professional.

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