F 550 4WD Super Duty V8-7.3L DSL Turbo VIN F (2001)
Glow Plug Relay: Description and Operation
Federal
Glow Plug Relay Control - Federal
The Glow Plug (GP) Relay Control is used to energize the glow plugs for assisting cold engine start-up. Engine Oil Temperature, battery positive
voltage (B+), and Barometric Pressure (BARO) are used by the PCM to calculate glow plug on-time and the length of the duty cycle. On-time
normally varies between 1 and 120 seconds. With colder oil temperatures and lower barometric pressures, the plugs are on longer. If battery voltage is
abnormally high, the duty cycle is shortened to extend plug life. (The glow plug relay will only cycle on and off repeatedly when there is a system high
voltage condition greater than 16 volts.)
An open in the glow plug relay circuit will render the glow plugs inoperative. A short circuit will result in a glow plug's always ON condition.
