1. Check the Fuses:
* Locate the fuse box: This is usually under the hood or under the dash. Consult your owner's manual for the exact location and a fuse diagram.
* Identify the fuses for power windows and door locks: They'll likely be labeled, or the manual will indicate which fuses control these circuits.
* Inspect the fuses visually: Look for blown fuses (a broken filament inside). Replace any blown fuses with fuses of the *same amperage*. Don't use a higher amperage fuse – this is a fire hazard.
2. Check the Battery and Connections:
* Battery voltage: Use a multimeter to check the battery voltage. It should be around 12.6 volts when the engine is off. A low voltage can cause intermittent or complete failure of electrical components.
* Battery terminals and cables: Check for corrosion, loose connections, or broken wires at both battery terminals and where the cables connect to the chassis. Clean any corrosion with a wire brush and baking soda solution. Tighten any loose connections.
* Ground connections: A poor ground connection can also cause widespread electrical problems. Look for ground straps connected to the chassis and make sure they're clean and securely fastened.
3. Check the Power Window Switch and Door Lock Switch Assemblies:
* Inspect the switches: Carefully examine the switches for any visible damage, broken wires, or loose connections. Try wiggling the switches gently while someone tests for power at the other end (see step 4).
* Test continuity (advanced): If you have a multimeter, you can test the switches for continuity. There should be a closed circuit when the switch is activated.
4. Check for Power at the Motors (Advanced):
* Locate the window motor(s) and door lock actuator(s): These are usually within the doors themselves. Accessing them might require removing door panels.
* Use a multimeter: With the switches activated, check if voltage is reaching the motors and actuators. If there's no power at the motors, the problem is likely before the motors – in the wiring, fuses, or power source.
5. Check the Wiring Harness:
* Inspect wiring: Look for damaged, frayed, or corroded wires in the door wiring harnesses, particularly where the wires enter the door jambs (common wear points).
* Trace the wiring: Follow the wiring back from the motors and switches to see if you can identify any breaks or shorts.
6. Central Locking Module (If Equipped):
* Some later-model S10s might have a central locking module. If yours does, this module could be faulty. Finding and testing this module requires more advanced electrical diagnostic skills.
Important Considerations:
* 1986 S10s are older vehicles: Their wiring might be brittle and prone to failure. Careful inspection is crucial.
* Safety: Disconnect the battery negative terminal before working on any electrical components to prevent accidental shorts.
* Professional help: If you're not comfortable working with car electrical systems, take your truck to a qualified mechanic. Troubleshooting electrical problems can be challenging.
By systematically checking these areas, you should be able to pinpoint the cause of your power window and door lock failure. Remember to consult a wiring diagram specific to your 1986 Chevy S10 2.8L for accurate fuse locations and wire tracing.
