1. Check the Blower Motor Resistor: This is the most likely culprit. The resistor pack regulates the speed of the blower motor. On high speed, it bypasses the resistor entirely. A faulty resistor will often result in only high speed working.
* Location: The resistor is usually located behind the glove box or under the dash, near the blower motor. Consult a repair manual specific to your 1991 Lincoln Town Car for its exact location.
* Testing: You can visually inspect it for burned components or broken wires. A multimeter can be used to test the resistance across the various terminals; however, this requires some electrical knowledge and the correct resistance values for each speed setting (found in a repair manual). The simplest test is visual inspection. If it looks damaged, replace it.
* Replacement: Replacing the blower motor resistor is relatively straightforward. Disconnect the wiring harness, remove the old resistor, and install the new one.
2. Check the Blower Motor Wiring Harness: Inspect the wiring harness connecting to the blower motor resistor and the blower motor itself for any broken wires, loose connections, or corrosion. Repair or replace any damaged wiring.
3. Check the Blower Motor Switch (Even Though You Replaced the Panel): While you replaced the climate control *panel*, the blower motor switch itself *might* be a separate component within the panel assembly, or even a separate unit altogether (depending on the car's design). It's possible a problem exists with the switch itself, even if a new panel was installed. If the switch is separate, test its continuity.
4. Check the Blower Motor itself (Less Likely): It's less likely, but possible the blower motor is failing. While unlikely to cause *only* high speed to function, a failing motor *could* exhibit strange behavior. Testing the motor requires removing it and checking its operation directly with a power source (exercise caution!).
5. Consult a Repair Manual: A 1991 Lincoln Town Car repair manual (either physical or online) will provide diagrams and specifications to help you accurately identify and test the components mentioned above. This is crucial for accurate diagnosis.
Important Safety Precautions:
* Disconnect the battery negative terminal before working on any electrical components.
* Be aware of sharp edges under the dash.
* If you are not comfortable working with car electrical systems, it's best to take your vehicle to a qualified mechanic.
Start with the blower motor resistor – it's the most probable cause given your symptoms. If replacing that doesn't solve the problem, move on to the other steps. Remember to consult that repair manual for specific locations and testing procedures for your model.
