Glow plugs are small heating elements that are used to help start diesel engines. They are located in the engine’s cylinders and heat the air inside the cylinder to make it easier for the diesel fuel to ignite. Glow plugs are typically only used when the engine is cold, as the heat from the engine itself is usually enough to ignite the fuel once the engine is running.
There are a few different ways to check glow plugs. One way is to use a multimeter to measure the resistance of the glow plugs. Another way is to use a test light to check if the glow plugs are getting power. If the glow plugs are not getting power, the problem may be with the glow plug relay or the wiring.