* Blower Motor Resistor: This component controls the speed of the blower motor. If it fails, it can create a short circuit, providing constant power to the motor even when the ignition is off. This is the most common cause.
* Blower Motor Switch: A faulty blower motor switch can similarly cause a short circuit, supplying power continuously. The switch itself might be failing internally, allowing power to bypass its normal control function.
* Wiring Harness: Damage or a short circuit within the wiring harness leading to the blower motor or the resistor can also cause the persistent operation. Look for frayed wires, damaged insulation, or signs of rodent activity.
* Relay (less likely): While less probable, a stuck or faulty relay in the blower motor circuit could continuously supply power.
Troubleshooting Steps:
1. Safety First: Disconnect the negative battery terminal before attempting any repairs. This prevents accidental shocks and short circuits.
2. Check the Resistor: Locate the blower motor resistor (often under the dash, near the blower motor). Visually inspect it for any signs of burning, melting, or damage. A simple multimeter test can confirm its functionality, checking for continuity and resistance values according to the vehicle's specifications. (You might need a wiring diagram for this.)
3. Check the Blower Motor Switch: The switch is usually located on the dashboard. Disconnecting it (after disconnecting the battery!) might stop the motor. If it does, the switch is likely the culprit.
4. Inspect the Wiring: Carefully examine the wiring harness leading to the blower motor and resistor for any signs of damage or fraying. Repair or replace any damaged wires.
5. Check the Relay (if applicable): If you suspect a relay, find the appropriate relay (consult your owner's manual or a wiring diagram). You can test it with a multimeter or simply swap it with a known good relay of the same type (if you have one).
Important Note: If you're not comfortable working with automotive electrical systems, it's best to take your Oldsmobile to a qualified mechanic. Improperly diagnosing or repairing electrical issues can lead to further damage or even fire.
