Glow Plugs: I-Mark

When engine coolant is below 140°F (60°C), No. 1 relay closes when ignition switch is turned to "ON" position. This supplies battery voltage to heat glow plugs quickly. No. 1 relay will open after about 2.5 seconds when specified temperature of 1562°F (850°C) is reached.

The No. 2 relay should close as ignition switch is turned to "START" position. The No. 1 relay will remain on when the ignition switch is turned to "START" if glow plugs have not reached specified temperature. At normal operating temperature, No. 1 relay will open when ignition switch is turned from "START" to "ON" as long as charging relay has been activated by alternator.