Glow Plug Inhibit Switch

The LL 4 (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 the color of their cap. A switch with a Black cap is a temperature-controlled switch. A switch with a Natural cap color is an optional switch which is always closed, allowing for more frequent cycling of the glow plugs.