1. Identify the Fan:
* Is it the blower motor itself or a separate AC clutch fan? The blower motor is inside the dash and moves air through the vents. The AC clutch fan is mounted on the radiator and only runs when the AC compressor is engaged. This troubleshooting focuses on the blower motor since that's most likely culprit given the description.
2. Check for Power:
* Disconnect the blower motor connector: With the ignition off, carefully disconnect the electrical connector going to the blower motor. If the fan stops, the problem lies in the wiring or the connector itself.
* Test for power at the connector: Use a multimeter to check for voltage at the blower motor connector with the ignition off. If you have power, you've narrowed down the problem to the wiring, the connector, or a short in the blower motor itself.
3. Wiring Diagnosis:
* Trace the wiring: Follow the wiring harness from the blower motor back to the controls under the dash. Look for any damaged, frayed, or corroded wires. Pay particular attention to any areas that might experience vibration or heat.
* Check the relay: There's likely a relay involved in controlling the blower motor. Locate the relay (consult your Corvette's wiring diagram – these are available online) and check for any signs of damage or corrosion. You might even swap it with a known-good relay (same amperage and configuration) to test it.
* Inspect the resistor pack (if applicable): Some models have a resistor pack that controls different blower speeds. A faulty resistor pack could potentially cause the fan to run even when the ignition is off.
* Check the blower motor switch: The switch itself could be faulty, allowing power to reach the blower motor even when it shouldn't.
4. Ground Issues:
* Poor ground connection: A bad ground connection can cause all sorts of electrical gremlins. Check the ground wires connected to the blower motor and the overall dashboard ground. Clean any corrosion and ensure tight connections.
5. Control Module (Less Likely):
* The climate control module itself could be malfunctioning, although this is less likely to cause the fan to run continuously. This is a more advanced repair and might require professional help.
Important Considerations:
* Wiring Diagrams: Obtain a wiring diagram specific to your 1986 Corvette. This is crucial for tracing wires and identifying components correctly. Several online resources offer these diagrams.
* Safety: Disconnect the battery's negative terminal before working on any electrical components. This prevents accidental shorts and shocks.
* Professional Help: If you're uncomfortable working with car electrical systems, it's best to take your Corvette to a qualified mechanic.
By systematically checking these areas, you should be able to pinpoint the cause of your 1986 Corvette's AC fan problem. Remember to always prioritize safety and consult a wiring diagram for accurate component identification.
