DIESEL GLOW PLUG SYSTEM OPERATION

Information provided in the 1984 Service Manual indicates that the thermal control in the glow plug controller allows current to flow continuously to the relay, thus preventing the glow plugs from cycling. This is incorrect, the 1984 system may cycle. Voltage to the controller that exceeds 13 volts will cause the controller to shut off current to the glow plugs. The current will stay off for a few seconds and then come back on. If the current still exceeds 13 volts it will continue to cycle on and off. A voltage that exceeds 13 volts will normally only occur when the alternator is charging. The glow plugs will then cycle on and off for a short period of time. Ths is considered a normal condition.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.