DIESEL: GLOW PLUG CONTROL MODULE FAILS (TIMER REPAIR)

VEHICLES AFFECTED: 1984-85 Models With 4.3L or 5.7L Enqines

1984-85 model diesels use a control module that contains a timer module and a relay. There have been cases where control module malfunctions were the result of an open circuit in the unit. This is particularly true of intermittent problems with the glow plug system. To correct this condition, remove the glow plug module from the car and remove the cover and the timer module as shown in Figure 1.

Visually examine the timer module for any evidence of damaged components or circuits. If no problems are noted, proceed as follows:

Pull the relay wires out of both clips. Scrape the end of the wires to remove the coating. Supply a ground to one end of the relay wire and then momentarily place 12 volts to the other end to make sure the relay works. (The sound and motion of the relay working is very evident). If the relay works, position the scraped end of the wires down into the clip area as shown in view A of Figure 1 and reinstall the timer module. Solder the prongs of the timer module to the clips and the wire. Reinstall the cover and reinstall the unit on the car.

Place a test light across the relay terminals, turn on ignition key and check system operation. Make sure the wait light operates satisfactorily and the test light goes out after the engine has been started.

Warranty Information - add .1 hour to the published time to solder coil wires.

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.