Mercedes-Benz ML400 Ignition Switch Replacement Cost

The ignition switch is part of the starting, charging and ignition systems. When turned, the ignition switch turns these systems on, allowing the vehicle to start and run. It also acts as a power switch for many of the electronic components in the car, including the radio, as well.

When the electrical portion of the ignition switch fails, the vehicle will permanently or intermittently lose power to certain systems and components, depending on which position the key is in. The vehicle may not turn on accessories like the air conditioner, or the vehicle may fail to start. In intermittent cases, the vehicle may randomly fail to respond to the key being turned, or stall while driving. These symptoms may come and go for some time before the ignition switch completely fails.

When ignition switch issues arise, it will be dangerous or impossible to drive the car. Depending on the point of failure, the vehicle could leave you stranded, stall in traffic, or even fail to turn off the engine when the key is removed. You should have the ignition switch repaired as soon as possible.

Most cars and trucks won't have issues with the ignition switch, but if they occur, they typically happen to older, high-mileage vehicles.

Because ignition switch problems are rare, a mechanic will typically check several other components before assuming it's the culprit. First, fuses and relays will be looked at. Then the starting and charging system may be checked, depending on the symptoms. If the other components of the starting and charging system are functioning properly, the ignition switch will likely be suspected. To check the switch, the technician will test voltages as the switch is moved to various positions. If it's not working as it should be, the switch will be replaced.

If the ignition switch and ignition lock cylinder are one component, replacing the switch will be very difficult if lock cylinder fails. If the lock cylinder works properly, the ignition switch is generally not too hard to remove. In most cases, the steering column plastic covers will be removed, and the lock cylinder will be turned and released. The ignition switch can then be taken out, after removing any obstructing or retaining hardware. Once the ignition switch is removed, a final bench test may be conducted to make sure it's the problem. The new switch will be installed and the lock cylinder will be put back in place. 

Replacing the ignition switch does not normally require replacement of the ignition switch lock cylinder, so the same key is normally used. If the lock cylinder is replaced, the ignition key will change as well.

The ignition switch is typically not a DIY job. Newer ignition switches have more advanced security systems and are more difficult to access or remove. With most modern vehicles, it's best to take it to a technician.