What’s the purpose of a preheating device?

Explanation: Most diesel engines have glow plugs to preheat the combustion chambers, so helping the engine to start when it's cold. When the ignition is switched on, the preheat warning lamp will show and the glow-plugs will rapidly heat up. In cold weather, the starter should only be operated when the glow plugs reach operating temperature and the warning light goes out.

Category: Vehicle Condition

References: The Official DVSA Guide to Driving Buses and Coaches: Section 2, The Official DVSA Guide to Driving Goods Vehicles: Section 4