DIESEL WAIT LIGHT RELAY INFORMATION

THERE HAS BEEN CONFUSION RELATIVE TO WHAT APPEARS TO BE TWO (2) RELAYS ON THE COWL OF A 1981 DIESEL-EQUIPPED 88, 98 OR TORONADO. ON 88'S AND 98'S, LOOKING FROM THE FRONT OF THE CAR TO THE COWL, THE UNIT ON THE RIGHT IS THE "WAIT" LIGHT RELAY. THIS RELAY HAS BEEN THE SAME SINCE 1978. SEE PAGE 259, FIGURE 1 FOR 88/98 IN YOUR 1981 ELECTRICAL TROUBLESHOOTING MANUAL. THE UNIT ON THE LEFT IS A DIODE MODULE, NOT AN IDLE RELAY, WHICH HAS BEEN DISCONTINUED. THE POSITION OF THESE TWO (2) UNITS ARE REVERSED FOR TORONADO. SEE PAGE 460, FIG. 2 IN THE ABOVE MANUAL. THE DIODES IN THE DIODE MODULE ARE NOT NEW TO THE DIESEL CIRCUITRY. THEY WERE IN THE WIRING HARNESS ON PAST MODELS, NOW TO IMPROVE SERVICEABILITY, THEY ARE IN A MODULE. THE MODULE CONTAINS THREE (3) DIODES WHICH ARE PART OF THE CHARGING CIRCUIT AND GLOW PLUG CIRCUIT. THEY PREVENT UNWANTED CIRCUIT FEEDS WHICH, IF BAD, COULD CAUSE THE FOLLOWING. 1.GENERATOR LIGHT WON'T GO OUT. 2.CAR WON'T SHUT OFF WITH KEY. TO TEST A DIODE MODULE, ALL THAT IS NEEDED IS A SELF-POWERED TEST LIGHT. 1.CONNECT GROUND CLIP TO TERMINAL "C" AND TOUCH THE OTHER PROBE END TO TERMINALS "A", "B" AND "D". THE LIGHT SHOULD LIGHT. IF NOT, REPLACE THE MODULE. 2.REVERSE TEST LEADS AND PERFORM SAME TEST. THE LIGHT SHOULD NOT LIGHT. IF THERE IS A LIGHT, REPLACE THE MODULE.

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.