* Blown Fuse: Check your owner's manual to locate the fuse for the blower motor and verify its integrity. A blown fuse is the easiest and cheapest fix.
* Resistor Pack: This is the most common cause. The resistor pack controls the different fan speeds. When it fails, you usually only get high speed (because that speed bypasses the resistor). The resistor pack is usually located behind the glove box or under the dash. Accessing it may require removing parts of the dashboard. You'll need to visually inspect it for burn marks or other damage. Replacement is relatively inexpensive.
* Blower Motor Switch: The switch itself could be faulty. It's less likely than the resistor pack, but possible. Testing this requires some electrical knowledge and a multimeter to check for continuity and proper voltage at different switch positions.
* Wiring Issues: Damaged or corroded wiring between the switch, resistor pack, and blower motor can interrupt the lower speed signals. This requires careful inspection of the wiring harness. Look for any breaks, fraying, or corrosion.
* Blower Motor: While less likely to only cause high-speed operation, a failing blower motor could exhibit this symptom. However, a failing motor usually results in weak performance at *all* speeds or complete failure.
Troubleshooting Steps:
1. Check the fuse first: This is the quickest and easiest thing to do.
2. Inspect the resistor pack: If the fuse is good, this is the next most likely culprit. Access it, visually inspect it, and replace it if necessary. This is a relatively inexpensive part.
3. Check the wiring: Carefully examine the wiring harness connecting the switch, resistor, and motor for any damage.
4. Test the blower motor switch (advanced): This requires a multimeter and some electrical knowledge. If you're not comfortable with this, take it to a mechanic.
5. Test the blower motor (advanced): Again, this requires electrical testing to ensure the motor is receiving power and functioning correctly.
Recommendation: Start with the fuse and then move on to the resistor pack. If you're not comfortable working on automotive electrical systems, take your Town Car to a qualified mechanic. They can quickly diagnose the problem and perform the repair. Replacing the resistor pack is often the solution, and it's usually a relatively inexpensive and straightforward repair for a mechanic.
