Glow Plug Functionality Check

The first thing to check for proper operation of the pre-heating system is that the glow plugs are powered by the corresponding relay: this check can be performed using a simple test lamp or a multimeter. Connect one end of the test lamp to ground and the other to the glow plug: when the ignition is turned on, the glow plug indicator light and the test lamp will illuminate, and when the indicator on the dashboard goes out, the test lamp will remain lit for a few more seconds before turning off. The same check can be repeated by setting the multimeter to the 20 Volt DC scale, connecting one end to ground and the other to the glow plug; in this case, when the ignition is turned on, the multimeter will indicate the voltage supplied to the glow plugs, which will then drop to zero after a few seconds once the dashboard indicator has turned off. Once confirmed that the power supply is correct, ensure that the glow plugs are functioning: being resistors, check that they are not broken and that their resistance value is correct; continuity can be checked using the test lamp; disconnect the power eyelet, connect the test lamp to the positive of the battery and the other end to the glow plug: if the lamp lights up, the glow plug is not broken; to measure its electrical resistance, set the multimeter to the 200 ohm scale, connect one end to ground and the other to the glow plug: a functioning glow plug should have an electrical resistance value of less than 2 ohms. Finally, you can remove the glow plug (blow around its seat to eliminate dirt that could enter the cylinder) and power it with two battery cables to check that the bulb glows uniformly. Apply copper grease to the thread before installing the glow plug.