* Faulty Blower Motor Resistor (despite replacement): While unlikely if you just installed a new one, it's possible the new resistor is defective. Double-check the part number against the correct one for your vehicle and make sure it's installed correctly. A bad connection is also possible.
* Wiring Issues: The most probable cause. Look for:
* Broken wires: Inspect the wires leading to and from the blower motor resistor. Look for any breaks, chafing, or corrosion, especially where the wires connect to the resistor and the blower motor.
* Loose Connections: Ensure all connections are secure and properly seated. Corrosion can interfere with a good connection even if the wire appears intact. Clean the connectors with a wire brush or electrical contact cleaner.
* Short Circuit: A short circuit somewhere in the wiring harness can prevent lower speeds from working. This requires more detailed electrical testing.
* Blower Motor Problems: Although less likely, a failing blower motor could cause this. While it works on high, the motor might not have enough power at lower speeds due to internal wear.
* Incorrect Replacement Resistor: The resistor might not be the correct one for your model. Double and triple check this.
* Control Module/Switch: While less common, a problem with the blower motor control module (often integrated into the climate control unit) could also be at fault. This is the least likely if the high speed works.
Troubleshooting Steps:
1. Verify Resistor Installation: Carefully remove the newly installed resistor and visually inspect it for any damage. Ensure it's securely connected. If you can, test its continuity with a multimeter (following appropriate safety precautions).
2. Inspect Wiring: Thoroughly inspect all wiring related to the blower motor and resistor. Pay close attention to the connectors. Look for any damage, corrosion, or loose connections. Use a multimeter to test for continuity in the wiring.
3. Test Blower Motor: If possible, test the blower motor directly with power (using caution!) to rule out a failing motor.
4. Check Fuses: Ensure the relevant fuse(s) haven't blown.
5. Advanced Diagnostics: If the above steps don't resolve the issue, you might need a multimeter and a wiring diagram for your specific Dodge Stratus to pinpoint the short or faulty component. A professional automotive mechanic may be necessary at this point.
Remember safety first when working with car electrical systems. Disconnect the battery negative terminal before working with any wires or components.
