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CRUISE CONTROL SYSTEMSForewordThis booklet is supplied by GM Product Service Training to GM dealer service personnel upon their com pletion ofthe subject course conducted at GM Training Centers.While this booklet will serve as an excellent review of the extensive program presented in the training centersession, it is not intended to substitute for the various service manuals normally used on the job. The range ofspecifications and variation in procedures between carlines and models requires that the division service publica tions be referred to, as necessary, when perform ing these operations.All inform ation contained in this booklet has been furnished by AC Spark Plug Division and Cadillac Motor CarDivision, General Motors Corporation. The inform ation is based on the latest data available at the time ofpublication approval. The right is reserved to make product or publication changes, at any time, w ithout notice.This booklet, or any portion thereof, may not be reproduced w ithout written consent of GM Product ServiceTraining, General Motors Corporation.

Table of ContentsPagePageNon-resume Type Cruise Control. . . . 1-1111.General O pe ra tio n . . . . 1-1Cruise System C om ponents. .1 - 3Component F u n c tio n s . .1 - 3Electrical and Vacuum O p e ra tio n . .1 - 6Electrical Operation . . . . 1-6IV.Vacuum Operation . .1 - 7System Diagnostics and S ervice. . . . 1-101. Cruise System Inoperative .1-102. Cruises Over/Under Set Speed . . .1-123. S u rg in g .1-13Electrical System S c h e m a tic .1-15Vacuum System Schematic .1-19Combined Electrical-Vacuum SystemS c h e m a tic .1-20Resume Type Cruise Control.2-1General O pe ra tio n .2-1Cruise System C o m p on e nts.2-1System Diagnostics and S ervice .2-21. Cruise System Inoperative .2-22. Cruises Over/Under Set Speed . . . . . . 2-23. S u rg in g . . . . 2-2Electro-pneumatic System Schematic . . . . 2-6V.Aspirator Assisted Vacuum System(J-car).3-1General O p e ra tio n .3-1System Diagnostics .3-2Vacuum System Schematic .3-4Vacuum Assisted Systems .4-1General Operation and Applications —4-1System Diagnostics .4-2Diesel Transducer, Non-Resume andResume Systems. . . 5-1Id e n tific a tio n . . . . 5-1System Diagnostics . . . 5-1VI.Electronic Cruise Control. . . . 6-1Non-D.F.I. and Computer IntegratedD.F.I., Cadillac . . . 6-1General Description . . . 6-1Component O p e ra tio n . . . . 6-2Typical C ircuit Operation, Non-D.F.I—. . . 6-8Typical C ircuit Operation, D.F.I. . . 6-13Diagnosis, Non-D.F.I. . . . 6-14Cruise Diagnosis, D.F.I. . . 6-18

I. Non-Resume Type CruiseControl (1968-1980 models)qGeneral OperationThe AC Cruisemaster System allows the driver tomaintain a constant highway speed w ithout having toapply continual foot pressure to the accelerator pedal.Selected cruise speeds are easily maintained. Speedchanges may be accom plished at w ill and overridefeatures allow the vehicle to be accelerated, slowedor stopped.To engage cruise control, the driver merely acceler ates to the desired cruise speed above 30 mph andthen fully depresses and slowly releases the controlswitch button. For ease of operation, the controlswitch button is located in the end of the turn signallever or gear shift lever (figure 1-1).Figure 1-1, Non-Resume Type Cruise ControlTurn Signal Handle and Switch.When engaged the cruise system controls throttle po sition. Vehicle speed is maintained regardless of ter rain changes. However, extremely steep hills, heavilyloaded vehicles and significant changes in altitudemay cause some variation in selected cruise speed.1. DEPRESS FULLY TO DISENGAGE2. PARTIAL RELEASE TO ENGAGE3. FULL RELEASE, CRUISE REMAINS ENGAGEDRefer to figure 1 -2. When the control switch button isheld in the completely depressed position it w ill dis engage the cruise control function. It will remain dis engaged as long as held depressed. When the buttonis partially released, it engages cruise control. Whenthe button is released the cruise control function re mains engaged.Some GM vehicles feature an “ ON-OFF” switch. Onthese models, the cruise control function may be dis engaged by placing the switch in the “ OFF” position.Figure 1-2, Operation Control Positions. O-ea-C/Ip M Z k r , tXa. 2 JLir "a eM(MU-*fi& Z O L A rv ft1/ i f L O B

I. Non-Resume Type Cruise ControlThe cruise control function is disengaged whenever the brake pedal is depressed (figure 1 -3a). To re-engage thecruise function, the driver merely accelerates to a speed above 30 mph and then fully depresses and slowlyreleases the control switch button.To cruise at a higher speed after cruise control has been engaged, the driver accelerates to the higher speed andthen fully depresses and slowly releases the control switch button.To cruise at a lower speed, fully depress the control switch button and hold it until the vehicle has decelerated tothe desired lower speed. Slowly releasing the control switch button re-engages the cruise function.When the cruise function is engaged, depressing the accelerator w ill override the system allowing vehicle speedto increase (figure 1 -3b). Releasing the accelerator pedal allows speed to decrease until it reaches the previouslyselected lower cruise speed. The cruise system will then autom atically maintain the previously selected speed.Figure 1 -3a, The Brake Disengages the System.Figure 1 -3b, The Accelerator Overrides theSystem.

I. Non-Resume Type Cruise ControlCruise System ComponentsThe major components of the AC Cruisemaster System are the engage switch, transducer assembly, servo andlinkage, vacuum and electric cruise release switches, the upper and lower cable and casing assemblies, wiringharness and vacuum lines (figure 1-4).Figure 1 -4, AC Cruisemaster System Components.Component Functions1. Cruise Control Switch (figure 1 - 5 ) . . .This driver operated control is convenientlymounted on the end of the turn signal handle orthe gear shift selector lever. The driver operatedfunctions of the cruise control switch have beenpreviously described in detail on page 1-1.Figure 1-5, Cruise Control Lever with EngageSwitch Button.1-3

— 1 -0-.I. Non-Resume Type Cruise ControlTransducer (figure 1 - 6 ) . . .The transducer is a com bination speed sensingdevice and control unit. It contains a low speedswitch that prohibits cruise control operation atlow speeds. This switch is calibrated at approxi mately 30 mph.SPEEDOMETERCABLEHOLDENGAGEWhen the cruise control function is engaged, thetransducer senses vehicle speed and controls thevacuum level to the servo to maintain the cruisespeed selected.PO R T“B”(TO MANIFOLDVACUUMSOURCE)P O R T“A”cs- c-d *z L*\ l-1 s&-crc y . y C jZ rib/Figure 1-6, AC Cruisemaster (non-resume type)Transducer.Servo, (figure 1 - 7 ) . . .The servo unit is connected to the carburetor by arod or linkage, a bead chain, or a Bowden cable orcom bination Bowden cable bead chain linkage.The servo unit maintains desired vehicle speed byreceiving a controlled am ount of vacuum from thetransducer. This vacuum adjusts the tension on therod, bead chain or other connection to the car buretor which controls throttle positioning.& y Figure 1-7, Servo unit.4. Combination Cruise Release Electric Switch andVacuum Release Valve (figure 1-8). .Whenever the brake pedal is depressed the electriccruise release switch disengages the system. As anadditional feature, the vacuum release valve alsodisengages the system when the brake pedal ispressed. Both of these controls are mounted onthe brake pedal bracket.BRAKE PEDALBRACKETBRAKEPEDALFigure 1-8, Brake Activated Electric andVacuum Cruise Release Controls.1-4

I. Non-Resume Type Cruise Control5. Com bination Vacuum Release Valve and Trans m ission Lock-up Torque C onverter Clutch Switch,Resume System Only (figure 1 - 9 ) . . .1981 and later model vehicles, equipped with alock-up torque converter (locking clutch) trans mission, use a com bination vacuum release valveand cruise release electric switch assembly.When the brake pedal is depressed, the vacuumrelease valve disengages the cruise function. At thesame time the contacts in the electric switch openwhich disengages the locking clutch mechanism inthe transmission. The locking clutch system w illremain disengaged after the brake pedal is re leased. The system remains disengaged until theelectronic control module signals re-engagement.1981 and Later Models Equipped withLock-up Torque Converter Transmission.See figure 1 -9. Whenever the vacuum release valveis adjusted it also adjusts the position of the lock up torque converter clutch switch.Upper and Lower Cable and Casing Assem blies (figure 1 - 1 0 ) .The upper cable and casing assembly connects the transducer to the speedometer. The lower cable andcasing assembly connects the transmission driven gear to the transducer.

I. Non-Resume Type Cruise ControlElectrical and VacuumOperationFigure 1-27 is a combined electrical-vacuum system schematic of the non-resume type cruise control system.Figures 1-25 and 1-26 show the electrical and vacuum systems separately.Electrical OperationOpen the fold-out page Electrical System Schematic, figure 1-25, page 1-15. The follow ing paragraphs de scribe the electrical operation of the system. Trace and follow circu it operation on the schem atic drawing.Current from the positive side of the “ BATTERY” (B ) flows through the “ IGNITION SWITCH” , “ FUSE” , closed“ BRAKE RELEASE SWITCH” to the “ CRUISE CONTROL SWITCH” .When the “ CRUISE CONTROL SWITCH” is in the “ AT REST” position, current flows through the switch, the “ 40OHM RESISTANCE WIRE” and to the “ HOLD” terminal on the “ TRANSDUCER” . The voltage at the “ HOLD”terminal is now quite low due to the voltage drop across the 40 Ohm resistance. This voltage is also applied to the“ SOLENOID COIL” in the tra n s d u c e r. . but it is not sufficient to energize this coil.Low Speed Switch Operation (figure 1 - 1 1 ) . . .The transducer contains a rubber clutch with anoperating arm. The clutch and arm rotate sim ilar to aspeedometer pointer needle. At speeds below approx imately 30 MPH, the clutch arm holds the low speedswitch contacts open.If the cruise control switch is depressed at speedsunder 30 MPH, the low speed switch contacts are heldopen by the clutch arm . . cruise can not beengaged.At speeds above about 30 MPH, the rubber clutch armrotates w hich allows the low speed switch contacts toclose (see dotted line, figure 1-11).When the low speed switch contacts are closed, thecruise system can now be engaged. The coil engageswith a distinct “ th u n k” sound.Refer to the electrical schematic, figure 1-25. Whenthe engagement switch button is released, currentflow through the “ 40 OHM RESISTANCE WIRE” is suf ficient to hold the “ SOLENOID” in the engagedposition.Cruise Lamp . .Some models of the cruise system feature a “ CRUISELAMP” (figure 1-25). When the “ SOLENOID” is en gaged it provides a ground for the cruise lamp. There fore, when cruise control is engaged the cruise lampwill illuminate.Figure 1-11, Low Speed Switch OperatingCircuit.

I. Non-Resume Type Cruise ControlVacuum OperationOpen the fold-out page, Vacuum System Schematic, figure 1-26, page 1-18. The follow ing paragraphs describethe vacuum operation of the AC Cruisemaster system. Trace and follow the circu it operating description on theschematic drawing.Assume the vehicle is operating at 50 MPH and the cruise control is not engaged. Vacuum from the enginemanifold is blocked off at “ PORT B ” of the “ TRANSDUCER” (figure 1-12 “ VIEW A ” ). A cup shaped valve which ispart of the “ SOLENOID” assembly is positioned to block “ PORT B” (also see figure 1-11).When the cruise control is engaged, the solenoid energizes, moving the cup shaped valve upward to also cover“ PORT A ” (figure 1 -12 “ VIEW B” ). With both ports covered, common vacuum is developed across “ PORT A ” and“ PORT B” .“VIEW A”PORT “B” BLOCKED,CRUISE NOT ENGAGED“VIEW B”PORT “A” AND PORT “B”COMMON VACUUM, CRUISE ENGAGEDFigure 1-12, Cup S haped Vacuum V alve Positioning

I. Non-Resume Type Cruise ControlWhen the solenoid is energized, engine vacuum ap pears at the “ SERVO” and the “ VACUUM BRAKE RE LEASE VALVE” . However, the amount of vacuumpresent must be precisely controlled. “ PORT C” is avariable orifice and is the control mechanism thatmaintains or adjusts vacuum level in the system, in cluding the “ SERVO” .SLIDING VALVEThe variable orifice, “ PORT C” consists of an orificetube and valve assembly. It is essentially an air meter ing valve that consists of a sliding valve, orifice tubeand a wishbone type clutch spring (figure 1-13).RUBBERCLUTCHFigure 1-13, Variable Orifice (Orifice Tube andValve Assembly).A rubber clutch is secured to a spindle shaft (figure1 -13). When the system is not in use, a solenoid oper ated “ CAM” mechanism (fold-out figure 1 -26) spreadsthe wishbone shaped clutch spring which allows therubber clutch to rotate w ithin th