1. Safety First:
* Disconnect the Battery: Before working on any electrical system, disconnect the negative (-) battery terminal to prevent accidental shorts or shocks.
2. Check the Obvious:
* Vacuum Leaks: Cruise control systems in that era often rely on vacuum. Check all vacuum lines connected to the cruise control system for cracks, loose connections, or leaks. Use a vacuum pump or your finger to test for suction. Leaking lines are a common cause of problems.
* Brake Switch: The brake switch is a crucial safety feature. When you press the brake, it should disengage the cruise control. If the brake switch is faulty, it might constantly interrupt the cruise control, preventing it from maintaining speed. Test the brake switch with a multimeter or replace it if it's suspect.
* Clutch Switch (if applicable): If your van is a manual transmission, a faulty clutch switch can also cause problems. The clutch switch should disengage the cruise control when the clutch pedal is depressed. Test this switch as well.
* Fuse: Check the fuse for the cruise control system in the fuse box. Replace it if blown.
3. Inspect the Cruise Control Components:
* Cruise Control Actuator: This is the component that actually controls the throttle. It's often located on the throttle body. Visually inspect it for damage or binding. Testing this often requires specialized tools and knowledge of its operation (it's usually a vacuum-operated diaphragm).
* Vacuum Reservoir (if equipped): Some systems have a vacuum reservoir to store vacuum for the cruise control. Make sure this is intact and not leaking.
* Speed Sensor: This sensor tells the cruise control system how fast the vehicle is going. A faulty speed sensor can prevent the cruise control from functioning properly. These can be tricky to test and often require a scan tool to confirm proper operation. Often located near the transmission or speedometer cable.
* Cruise Control Switch Assembly: Inspect the steering wheel-mounted switches for any signs of damage or loose connections. Try cleaning the contacts with electronic contact cleaner.
4. More Advanced Diagnostics (Requires Specialized Tools):
* Scan Tool: A scan tool can read diagnostic trouble codes (DTCs) from the vehicle's computer system. This might pinpoint the exact cause of the cruise control malfunction. Older vehicles may not have sophisticated onboard diagnostics, though.
* Multimeter: A multimeter can be used to test the voltage and continuity of the cruise control system's wiring and components. This requires a wiring diagram for your specific van model.
5. Repair or Replacement:
* Once you've identified the faulty component, you'll need to repair or replace it. Replacing vacuum lines is relatively easy. Replacing other components may require more mechanical skill.
Important Notes:
* Wiring Diagram: Obtain a wiring diagram for your specific 1992 Chevy van model. This is essential for tracing wires and testing the electrical components of the cruise control system. You can often find these diagrams online or at a parts store.
* Professional Help: If you're not comfortable working on your vehicle's electrical system or are unable to identify the problem, it's best to take it to a qualified mechanic. Improper repairs can lead to further damage.
Finding a reliable wiring diagram and a trustworthy repair manual specific to your van's year and model will greatly aid in this troubleshooting process. Good luck!
