1. Blower Motor Resistor: This component controls the fan speed. When it fails, the fan often runs at its highest speed continuously, regardless of the setting.
* Troubleshooting: Locate the blower motor resistor (usually under the dash, near the blower motor itself; consult your repair manual for the exact location). Inspect it visually for any signs of burning, melting, or damage. A simple continuity test with a multimeter can confirm if it's functioning correctly. If it's faulty, replacing it is relatively inexpensive and usually straightforward.
2. Blower Motor Control Module (Often part of the HVAC Control Panel): This module receives signals from the HVAC controls and regulates the blower motor. A malfunctioning module can cause the fan to run constantly. This is less likely than a resistor issue, but certainly possible.
* Troubleshooting: Diagnosing this requires more advanced techniques. A scan tool might reveal fault codes related to the blower motor or HVAC system. If you don't have a scan tool, replacing the entire control panel (which often houses the module) is a more involved repair, and it's more expensive.
3. Wiring Issues: A short circuit or a damaged wire in the circuit supplying power to the blower motor can also cause it to run continuously.
* Troubleshooting: This requires careful inspection of all wiring related to the blower motor, the resistor, and the control module. Look for frayed wires, broken insulation, or signs of corrosion. Repairing any damaged wiring is essential.
4. Blower Motor Switch: Less common, but a faulty blower motor switch could also be sending a continuous signal to the blower motor.
* Troubleshooting: This requires checking the switch for proper operation. You can try disconnecting the switch and seeing if the fan stops. If it does, the switch is likely the culprit.
5. (Unlikely but possible) Direct Short to the Blower Motor: A rare possibility is a direct short within the blower motor itself that causes it to run constantly.
* Troubleshooting: This is the least likely scenario, but if all other components check out, the blower motor might need to be tested or replaced.
Before attempting any repairs:
* Disconnect the battery's negative terminal. This is crucial to prevent electrical shocks and further damage.
* Consult a repair manual: A repair manual specific to your 2002 Chevy Express van will provide detailed diagrams and instructions for locating components and performing repairs.
If you're not comfortable working with car electrical systems, it's best to take your van to a qualified mechanic. Improper repairs can lead to further damage or even fire hazards.
