I checked for vacuum leaks the best I could. Saw a post that the switch sometimes just wears out... anybody know how I could test that?
Ohm meter if it is dual electric and vacuum test for a leak. It is mechanical!!!
Here is the most complete write up on the old XJ cruise control I have ever seen!!!
http://jeep-manual.ru/index.php?page=78
and Cruiser54 has a write up at
www.cruiser54.com as I recall
Jeep vehicles use an electro-mechanical servo system. The system consists of a control module, speed sensor, servo, control switch assembly, vacuum storage canister, check valve and release system. Release system consists of a mechanical vacuum vent valve and brake and clutch (M/T) release switches.
Cruise control switch is an integral part of turn signal switch lever and consists of 2 separate switches. First is an "ON-OFF" and "RESUME" slide switch located on flat of directional switch lever.
Second is "SET/COAST" push button switch located at end of directional switch lever. To engage system, move slide switch to "ON" position and accelerate to desired speed. Depress and release "SET/COAST" button on end of switch lever. System will now maintain selected speed.
System will automatically disengage when brake or clutch pedal is depressed. It can be re-engaged to previously selected speed by accelerating to 30 MPH and moving slide switch to "RESUME" position, then releasing switch.
NOTE: When slide switch is moved to "OFF" position, pre-set speed of "RESUME" function is canceled from memory and must be reset when system is reactivated.
Higher speed can be set by pressing on accelerator pedal until new speed is reached and then pushing "SET/COAST" button. Lower speed can be obtained by lightly depressing brake pedal, allowing the vehicle to slow to desired speed and then depressing and releasing "SET/COAST" button.
CONTROL MODULE
Control module receives input voltage representing vehicle speed from speed sensor, which is driven by the speedometer cable. Control module has a low speed circuit that prevents operation at speeds below 30 MPH. See Fig. 1.
SERVO
Servo is controlled by control module and uses manifold vacuum to control throttle. Bead-link chain connects servo cable to throttle linkage. See Fig. 1.
CONTROL SWITCH
Control switch assembly is an integral part of turn signal switch lever. See Fig. 1.
RELEASE SYSTEM
Release system deactivates cruise control system when brake or clutch pedal is depressed. Either servo vent valve or mechanical vacuum vent switch admits atmospheric pressure into servo when brake pedal is depressed.
TROUBLE SHOOTING
NOTE: Vehicles with computerized engine controls, should be tested for stored computer codes. Codes and related problems must be repaired prior to cruise control diagnosis and repair. For additional information, see COMPUTERIZED ENGINE CONTROLS section.
SYSTEM WILL NOT ENGAGE
Restricted vacuum hose or no vacuum. Control switch or control module defective. Speed sensor defective. Clutch or brake light switch defective or misadjusted. Brake light switch wire disconnected. Open circuit between brake light switch and brake lights.
RESUME FEATURE INOPERATIVE
Defective servo ground connection. Defective control switch. ACCELERATE FUNCTION INOPERATIVE
Accelerate circuit in control module inoperative. Defective control switch.
SYSTEM RE-ENGAGES WHEN BRAKE PEDAL IS RELEASED
Defective control module. Mechanical vent valve not opening. Kink in mechanical vent valve hose. Brake light switch defective.
CARBURETOR THROTTLE DOES NOT RETURN TO IDLE POSITION
Improper linkage adjustment. ROAD SPEED CHANGES 2 MPH OR MORE WHEN SETTING SPEED
Centering adjustment wrong. Servo link misadjusted.
ENGINE ACCELERATES WHEN STARTED
Improper servo chain adjustment. Vacuum hose connections reversed at servo. Defective servo.
SYSTEM DISENGAGES ON LEVEL ROAD WITHOUT APPLYING BRAKES
Loose wire connection. Loose vacuum hose connection. Servo linkage broken. Defective brake light switch.
ERRATIC OPERATION
Reverse polarity of system wiring. Defective servo. Defective control module.
VEHICLE CONTINUES TO ACCELERATE WHEN "SET" BUTTON IS RELEASED
Servo or control module defective. SYSTEM ENGAGES BUT SLOWLY LOSES SET SPEED
Air leak at connections or in vacuum hoses. Air leak on vent valve on brake pedal.
ADJUSTMENTS
CONTROL MODULE ADJUSTMENT
NOTE: Control module adjustments are preset by manufacturer. If
other components in system appear to be functioning properly
and cruise control remains inoperative, perform following adjustments to determine if control module is functional.
1) Remove control module attaching screws or tie straps and
move control module downward for adjustment access. Turn centering
adjustment screw to 10 o’clock position. Turn low speed adjustment
screw to 10 o’clock position. Turn sensitivity adjustment screw fully
clockwise.
CAUTION: Adjustment potentiometers are extremely delicate. Carefully insert screwdriver and do not push or turn screws excessively hard. Maximum movement is 3/4 turn.
- Adjustments are not precisely correct for vehicle, but are
acceptable to determine if control module is functioning. Perform
precise adjustments by road testing vehicle on level road. If
adjustments have no effect on cruise control, replace control module.
- If actual engagement speed is 2 MPH or more above selected
speed, stop vehicle and turn centering screw 1/16 of a turn
counterclockwise. Recheck engagement speed and adjust as necessary.
- If engagement speed is 2 MPH or more below selected speed,
turn centering screw 1/16 of a turn clockwise. Recheck engagement
speed and adjust as necessary.
VACUUM VENT VALVE
Depress brake or clutch pedal and hold in depressed position. Move vacuum vent valve toward bracket on pedal as far as possible. Release brake or clutch pedal.
TESTING
NOTE: Vehicles with computerized engine controls, should be tested for stored computer codes. Codes and related problems must be repaired prior to cruise control diagnosis and repair. For additional information, see COMPUTERIZED ENGINE CONTROLS section.
PRELIMINARY INSPECTION
Ensure cruise control wire harness is properly connected to
control module before starting diagnosis or repair procedure, as this connection is disturbed when Cruise Command System Tester (AM PC-1-R) is used. Poor connection at this point may be improperly diagnosed as control module malfunction.
Brake light and clutch switches should be properly adjusted. Ensure that all vacuum lines are correctly routed and tightly connected.
CRUISE COMMAND SYSTEM TESTS
Testing is performed with Cruise Command System Tester (AM PC-1-R). Remove wire harness connector from control module. Connect tester to wire harness connector. Perform tests as part of service diagnosis to determine cause and correction of system malfunction. Various tester lights are associated with specific components, circuits, etc.
CONTROL SWITCH CONTINUITY
Wrangler
NOTE: Voltage checks should show battery voltage. If resistance readings are incorrect, check circuit for an open or a short. Cruise control module terminal No. 1 grounds through connector at engine block.
Light No. 1 "OFF" (Set Switch)
With control switch in "ON" position, check for battery voltage between HAZ/STOP and in-line fuse, terminal No. 14 and ground terminal No. 1
Light No. 2 "OFF" (Control Switch & Speed Sensor) With control switch in "ON" position, check for battery voltage between HAZ/STOP and in-line fuse, terminal No. 5 and ground terminal No. 1. With ignition switch in "OFF" position, check resistance between terminals No. 2 and No. 3. Resistance should be 15-50 ohms.
Light No. 3 "OFF" (Brake Light Ground)
With ignition switch in "ON" position, install jumper wire between terminals No. 7 and No. 13. If brake lights do not turn on, check fuses and brake light switch connections.
Light No. 4 "OFF" (Throttle Position Feedback Sensor) With ignition switch in "ON" position, check for battery
voltage between gauge fuses at terminals No. 7 and No. 1.
With ignition switch in "OFF" position, check resistance
between terminals No. 2 and No. 11. Resistance should be 2400-4000
ohms. At idle resistance should be 2800-4300 ohms and at wide open
throttle resistance should be 4000 ohms.
Light No. 5 "OFF" (Resume/Accel/Vent Valve) With control switch in "RESUME/ACCEL" position, check for battery voltage between HAZ/STOP and in-line fuse, terminal No. 10 and ground terminal No. 1. With ignition switch in "OFF" position, check resistance between terminals No. 6 and No. 12. Resistance should be 30-50 ohms. Resistance between terminals No. 6 and ground, and terminal No. 12 and ground should be infinite (open).
Light No. 6 "OFF" (Resume/Accel/Charge Valve) With control switch in "RESUME/ACCEL" position, check for battery voltage between HAZ/STOP and in-line fuse, terminal No. 10 and ground terminal No. 1. With ignition switch in "OFF" position, check resistance between terminals No. 4 and No. 12. Resistance should be
30-50 ohms. Resistance between terminals No. 4 and ground, and terminal No. 12 and ground should be infinite (open).
WRANGLER CRUISE CONTROL TESTING
Conditions Lights "ON"
Control Switch "ON" & Set Switch Depressed No. 1
Control Switch "ON" No. 2
Ignition "ON" & Brake or Clutch Pedal Depressed No. 3 & No. 4
Cruise Control & Resume/Accel "ON" No. 5 & No. 6
Cruise & Resume/Accel "ON" & Engine Running (1) No. 5 & No. 6
(1) - Servo will pull throttle wide open. Keep RPM at a safe level by releasing cruise control switch.
Except Wrangler
Use 12-volt test light to test control switch continuity. Connect test light to wires as indicated in CONTROL SWITCH CONTINUITY TEST CHART. See Figs. 3 or 4.
That is just part of the write up on that site!!!
I may just finally try to get mine going for the first time. Never really tried to fix mine, always seemed very low on the priorities
