Glow Plug Relay: Description and Operation

Glow Plug Circuit:

Glow Plug Controller:

PURPOSE
The electronic glow plug controller relay assembly monitors and controls glow plug relay operation.

OPERATION
The assembly contains the circuitry which monitors and controls glow plug relay operation. Information received at pins B and C is used by the controller to determine glow plug operating requirements. Pin B senses voltage at the starting motor solenoid. Pin C senses glow plug voltage. the controller also senses ambient temperature.

A normally functioning system operates as follows:

Key on - Engine not running and at room temperature.

1. Glow plugs ON for 4 to 6 seconds, then OFF for about 4.5 seconds

2. Then cycle; ON for about 1.5 seconds, OFF for about 4.5 seconds, and continue to cycle 1.5 ON/4.5 OFF, for a total duration (including the initial 4 to 6 seconds) of about 20 seconds.

If the engine is cranked during or after this sequence, the glow plugs will cycle ON/OFF for a total duration of 25 seconds after the engine control switch is returned from the crank position, whether the engine starts or not. the engine does not have to be running to terminate the glow plug cycling.

All the times shown above are approximate because they vary with initial engine temperature. The initial ON time and cycling ON/OFF times vary also with system voltage and/or temperature. Lower temperatures cause longer duration of cycling.

LOCATION
The controller is mounted at the rear of the left cylinder head on two 10 mm studs.