Preheat light: why does it light up?

The warning light for preheating is installed on vehicles with a diesel engine. This is an orange-yellow light indicating the coil. It lights up when the ignition is turned on and indicates that the glow plugs are heating the cylinders. It should usually shut down after a few seconds.

🚗 What is the preheat indicator for?

Le preheat indicator This is a warning light that is only used in diesel vehicles. Indeed, it is associated with a preheating system that is not found on gasoline engines. On diesel engines, glow plugs play the role of heating the air in cylinders so that the machine can be started in a cold state.

The preheat indicator lights up orange; he is Coils horizontally and lights up on the dashboard when the ignition is turned on. You must wait for it to go out before starting to allow the temperature in the cylinders to rise to allow better diesel combustion and reduce vehicle pollution.

There is a difference between direct injection vehicles and indirect injection vehicles. On them, candles also work in after-sales service... To reduce pollution and noise, the glow plugs continue to heat up after starting until the engine reaches normal operating temperature.

In this case, the preheat indicator light is still off, unless it is defective. Another difference: the glow plugs are not located in the same place depending on the type of injection. With direct injection, the spark plug heats the air in the cylinder, while with indirect injection, it is in the pre-combustion chamber.

💡 Why does the preheat lamp come on?

When you turn on the ignition of your diesel vehicle, it is normal for the preheating warning light to come on. Indeed, it warns you about the preheating of the combustion chamber or its cylinders. Diesel vehicle drivers are advised to wait until the warning light goes off before starting.

This will ensure that your combustion chamber has reached the optimum temperature for your engine to function properly. you too Reduce pollution vehicle, but also to prevent premature clogging of your diesel engine components.

Thus, if the preheat lamp does not light up, it is, on the contrary, indicative of a malfunction. It should normally light up while the glow plugs are heating the air in the cylinders and then extinguish when the correct temperature is reached.

However, a glow plug warning light that comes on while driving or flashes also indicates a malfunction. If the preheat indicator stays on, you need to:

• Of the problem wire harness ;
• Due to rejection preheating relay ;
• From the problemampoule preheat indicator light;
• From anxiety at the level glow plugs ourselves, except for old cars.

For older vehicles, keep in mind that a glowing plug does not indicate a faulty spark plug. Electrical problem: harness, relay or light bulb.

🔍 Flashing preheat indicator: what to do?

During normal operation, the glow plug will light up to let you know that the glow plugs heat up the cylinders to make it easier to start the vehicle. It turns off when the temperature drops.

Un preheat indicator light flashes defective. Like a warning light that comes on while driving or stays on after starting, it can indicate a malfunction of the glow plug relay, the spark plugs themselves, or the electrical circuit.

If the glow plug warning lamp is blinking or on, and your vehicle is also experiencing a loss of power, there may be a problem with the injection circuit. Self-diagnosis should be performed.

⚙️ What if the preheat indicator is on?

If the preheat indicator comes on, then you are in one of the following two situations:

• The control lamp lights up when the ignition is turned on;
• The control lamp lights up or flashes while driving or remains on after starting.

The first case corresponds to the normal operation of the preheating warning lamp. In fact, it shows you the temperature of the cylinders using the glow plugs. Wait a few minutes that the indicator goes out before starting: starting will be easier, even in a cold state, and you will pollute the environment less.

On the other hand, a preheat warning light that stays on after starting, that flashes, that comes on while driving, but also does not come on at all, indicates a problem. On older vehicles, this is not a spark plug malfunction, but it is likely that your preheating relay malfunctions.

On newer vehicles, this could be a malfunctioning glow plug or an electrical problem. Occasionally, the activation of the preheating warning light indicates a malfunction of another origin, usually at the level of the injection circuit.

Therefore, if the preheat lamp comes on, you should go to the garage to diagnostic vehicle... This will allow you to determine the cause of the malfunction and take appropriate action by replacing the spark plugs, test lamp, preheat relay or any part causing the malfunction.

That's it, you know all about the glow indicator and its role! Like other indicators on your dashboard, it gives you information: in this case, the glow plugs went off. But it can also reflect a malfunction, the cause of which must be determined in order to be repaired without delay.