Skip the auto shop - Our mechanics make house calls

Q: Preglow indicator light on

asked by on

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Starting problems when the engine warms up

It's possible you have a leaking fuel injector - which is losing the residual fuel pressure in the fuel line. The fuel leaks into the cylinder, but leaves you with a partially filled fuel line. Diesel fuel injectors, when working...

Q: Alarm and keyless entry malfunction, G error code

Hey there, thanks for writing in about your 2007 Mercedes Benz E550. The car alarm in many of the later model Mercedes vehicles has it's own set of small batteries. When these batteries go bad, they will automatically set off the...

Q: Starter solinoid

Hi There, You may be correct in that you may have a faulty starter solenoid. As you may know, electricity is supplied to the starter a small gear comes out and engages the flywheel to spin the engine over as...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.