Glow Plug Inhibit Switch

The LL4 (heavy duty emissions version of 6.2L engine) is equipped with a glow plug inhibit switch. The inhibit switch is calibrated to open above 125°F (51.5°C) to prevent glow plug operation above this temperature.

Two types of inhibit switches are used. Switches can be identified by their cap color. A switch with a Black cap is a temperature-controlled switch. The other switch (with a non-Black cap) is an optional switch which is always closed to allow for more frequent cycling of glow plugs.