Mercedes Glow Plug Light

The Leading Garage in Thousand Oaks to Fix a Mercedes Glow Plug Relay Failure

By Bavarian Performance Specialists December 15, 2023

One common problem that Mercedes owners can face is a glow plug relay failure, which can affect the performance of diesel engines. Glow plugs are essential for starting a diesel engine, as they preheat the combustion chamber to aid ignition when the engine is cold. The glow plug relay is responsible for controlling the operation of these glow plugs.

When you turn the key to start the engine, the glow plug relay activates the glow plugs, which heat up the combustion chamber. This preheating process makes it easier for the engine to start, particularly in cold weather. After the engine has started, the glow plug relay deactivates the glow plugs, ensuring they don’t overheat.

Common Causes of Glow Plug Relay Failure

  • Age and Need for Replacement: Just like any electrical component, the glow plug relay can experience wear and tear over time. The constant activation and deactivation of the glow plugs can lead to wear on the relay’s internal components, causing it to fail.
  • Electrical Problems: Any electrical system can be vulnerable to issues like corroded connectors, damaged wires, or poor connections. In Mercedes diesel engines, these electrical issues can affect the proper functioning of the glow plug relay.
  • Overheating: The glow plug relay is often located in a high-temperature area of the engine bay. Over time, exposure to extreme engine temperatures can lead to overheating of the relay, which can cause it to malfunction.
  • Voltage Spikes: Electrical systems can sometimes experience voltage spikes, which can damage sensitive components like the glow plug relay. These voltage spikes may occur due to a failing alternator or other electrical system issues.
  • Contaminants: Diesel engines can produce soot and other contaminants, which can accumulate around the glow plug relay. These contaminants may interfere with the relay’s operation or cause damage over time.

Watch Out for These Indications of a Glow Plug Relay Failure

  • Hard Starting: One of the most common signs of a glow plug relay failure is difficulty starting the engine, particularly in cold weather. When the glow plug relay is malfunctioning, the glow plugs may not heat the combustion chamber effectively, making it harder for the engine to start.
  • Glow Plug Light Stays On: Most Mercedes vehicles equipped with glow plugs have a dashboard light that indicates when the glow plugs are active. If this light remains illuminated for an extended period or doesn’t turn off after starting the engine, it’s a sign that the glow plug relay may be failing.
  • Reduced Engine Performance: A failing glow plug relay can lead to reduced engine performance. You may notice slower acceleration, a decrease in power, or even an increase in exhaust emissions.
  • Poor Fuel Efficiency: As the glow plug relay is integral to the efficient combustion of diesel fuel, a malfunction can lead to poor fuel efficiency. You might notice a decrease in miles per gallon (MPG) and more frequent trips to the fuel pump.
  • Illuminated Check Engine Light: A malfunctioning glow plug relay can trigger the check engine light on your dashboard. It’s essential to have the vehicle’s diagnostic system scanned to identify the specific issue when the check engine light is illuminated.
  • Excessive Smoke from Exhaust: A failing glow plug relay can lead to incomplete combustion in the diesel engine. This incomplete combustion can result in increased exhaust smoke, often appearing as white or gray smoke coming from the tailpipe.

Bavarian Performance Specialists

A glow plug relay failure in your Mercedes can be a frustrating and problematic issue, particularly Mercedes Glow Plug Relay Checkin cold weather. Identifying the signs of a failing relay and understanding the common causes is the first step in addressing the problem. However, it’s essential to emphasize the importance of professional maintenance and repair.

Professional technicians possess the knowledge, experience, and tools necessary to accurately diagnose and address glow plug relay issues, ensuring that your Mercedes continues to provide the exceptional performance and reliability you expect from this iconic brand. So, if you notice any signs of a glow plug relay problem, don’t hesitate to consult with our certified technician to keep your Mercedes running smoothly. Visit us today from nearby Thousand Oaks, Agoura Hills, Westlake, Malibu, and Newbury Park, CA.