One common problem with Mercedes vehicles, especially during cold weather, is a slow or difficult engine start. If you start to experience this issue with your car, one of the culprits is the glow plug timer relay.
A faulty glow plug timer relay affects the engine’s starting ability, causing a delay and other engine problems. Knowing what signs to look for can help you save your engine before any real damage. In this guide, we will discuss the functions of the glow plug timer relay and how to know when it is due for replacement.
What is a Glow Plug Timer Relay?
Let us first understand what a glow plug timer relay is and why it is important. Your Mercedes engine has a glow plug, which is similar to a spark plug in a gasoline-powered vehicle. Both plugs heat up the air-fuel mixture in a car’s engine to provide the combustion energy required for the engine’s function.
However, the timer relay receives various inputs from other components of the combustion system to determine the time sequence for when the glow plug will preheat the air-diesel mixture. If this glow plug timer relay fails, ignition could become a problem in the affected vehicle.
The common causes of glow plug timer relay failure are:
- Normal wear and tear with continued use.
- External factors such as moisture and road salts cause corrosion.
- Poor electrical connections or damaged electrical system.
- Use of poor-quality materials.
- Faulty sensors that pass the wrong information to the timer relay.
- Poor maintenance or faulty repairs and replacements.
Common Signs to Indicate a Faulty Glow Plug Timer Relay in a Mercedes
When the glow plug timer relay in a car gets bad, the next step is to find a replacement to avoid further complications. Here are some common signs to help you identify when it is time for that timer relay replacement in your car:
Difficulty in Starting the Engine
One of the major signs of a faulty glow plug timer relay is when the car’s engine does not start easily. It could take several key turns for ignition to happen. This is because a bad timer relay could cause a delay in the preheating process, preventing the glow plugs from heating the air-fuel mixture properly.
Excessive Exhaust Smoke Production
Once you start to notice white smoke coming from your car’s exhaust, it could be that it is time to inspect the glow plug timer relay. A timer relay failure usually affects the heating process of the glow plugs, leading to incomplete combustion. This usually results in the production of excessive smoke from the affected car’s exhaust.
Dashboard Warning Lights
As with many other car faults, a damaged glow plug timer relay can trigger a warning light on the dashboard to come on. The dashboard glow plug light could illuminate once there is a fault with your car’s glow plug timer relay.
Reduced Fuel Economy
As a Mercedes owner, if you notice that your diesel consumption has increased without an increase in your traveling distance, it could be due to a bad glow plug-timer relay. A faulty relay timer affects the ignition process, which puts more load on the engine, thus increasing its demand for fuel.
Other signs include:
- Engine rough idling.
- The engine refuses to start, especially in cold weather.
- Engine misfiring.
- The glow plug indicator light stays on for longer than usual.
Where to Go in Michigan for Your Mercedes Glow Plug Timer Relay Replacement
If your car has been showing any of the above 
signs of a faulty glow plug timer relay, it is time to look for the best replacement option. Finding a mechanic with enough experience and equipment can give your car a better chance.
Motor City Euro Repair is a top Auto repair shop in Farmington. We know European vehicles and have well-trained and experienced technicians who can help fix any issue with your car. We also have flexible payment options to help relieve the burden of costly repairs, all to ensure your car gets the best care.
We extend our premium services to European car owners in Ann Arbor, Brighton, Detroit, and Farmington, MI. If you are in any of these locations, contact us today for excellent automobile care services.
* Mercedes-Benz GLC 300 4Matic Coupe Car image credit goes to: Julie Deshaies.
