BRAKE LIGHT VACUUM LEAK DIAGNOSIS

THE INSTRUMENT PANEL BRAKE WARNING LIGHT ON 1982 "C", "E", AND "K" CARS EQUIPPED WITH GASOLINE ENGINES MAY TURN ON DUE TO A VERY SLIGHT INTERNAL VACUUM LEAK IN THE LOW BRAKE VACUUM SWITCH LOCATED ON THE VACUUM BRAKE BOOSTER (REFER TO FIGURE 1). SHOULD THIS SLIGHT LEAK OCCUR, THE SWITCH IS DESIGNED TO TURN THE INSTRUMENT PANEL LIGHT ON. SINCE ALL OF THESE VEHICLES ARE EQUIPPED WITH AN AUXILIARY VACUUM PUMP, IN ADDITION TO THE ENGINE SUPPLIED VACUUM, THERE WILL BE ADEQUATE VACUUM UNDER ALL OPERATING CONDITIONS. A NEW DESIGN LOW BRAKE VACUUM SWITCH (REFER TO FIGURE 2) P/N 18010308, AVAILABLE THROUGH GMWDD, HAS BEEN RELEASED TO CORRECT THIS CONDITION. WHEN DIAGNOSING THIS CONDITION, PROCEED AS FOLLOWS: 1.WITH THE ENGINE IDLING AND THE TRANSMISSION IN PARK, DISCONNECT THE LOW BRAKE VACUUM SWITCH ELECTRICAL CONNECTOR. A.IF THE I.P. BRAKE WARNING LIGHT GOES OUT, PROCEED TO STEP 2. B.IF THE I.P. BRAKE WARNING LIGHT STAYS ON, REFER TO TELL-TALE LIGHT OPERATION CHECK, PAGE 5-5, AND PARK BRAKE LAMP, PAGE 8B-19, IN THE 1982 CADILLAC SERVICE INFORMATION MANUAL. ALSO REFER TO THE BRAKE WARNING SYSTEM CIRCUIT DIAGRAMS ON PAGES 84-89 OF THE 1982 ELECTRICAL TROUBLESHOOTING MANUAL. 2.REMOVE THE LOW BRAKE VACUUM SWITCH AND INSERT A NEW DESIGN SWITCH, P/N 18010308. CONNECT THE LOW BRAKE VACUUM SWITCH ELECTRICAL CONNECTOR. A.IF THE LIGHT DOES NOT TURN ON, THE CONDITION IS CORRECTED. (NORMAL OPERATION OF THE LOW BRAKE VACUUM RELAY DELAYS THE LIGHT FROM TURNING ON 30-40 SECONDS AFTER THE SWITCH'S CONTACTS CLOSE DUE TO A LOW VACUUM CONDITION.) B.IF THE LIGHT TURNS ON, CHECK THE VACUUM BRAKE BOOSTER AND ITS VACUUM HOSES FOR VACUUM LEAKS.

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.