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Q: Preglow indicator light on

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The preglow indicator light came on in my car. It is illuminated in orange and it turns on when I turn the key before the engine starts running. What does this light indicate? Are there any issues that might damage the car?

A: Your car has a diesel engine. Diesel engine...

Your car has a diesel engine. Diesel engines have no spark plugs, they rely on ultra high compression of the fuel, which is injected at precisely the highest air pressure in the cylinder, to ignite on it’s own based on the rise in temperature of the compressed air. When a diesel engine is cold this is more challenging. Glow plugs, tiny electrical coils inside the cylinder, heated by the car’s battery prior to starting, help the engine come up to operating temperature so that normal compression-based ignition occurs. The orange light you describe indicates that the glow plugs are coming on as designed. If you are experiencing and performance issues, have a certified technician inspect the car to pinpoint the issue.

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