1. Fuses and Relays:
* Check the fuses: Your owner's manual will show the fuse box location and diagram. Look for fuses related to the blower motor, HVAC, or the AC system. A blown fuse is the easiest and cheapest fix.
* Check the relays: Relays are electrical switches controlled by a low-current signal. They often fail before the fuse blows. Your owner's manual should indicate the location and function of relevant relays. You might need to swap a known good relay from a similar circuit (if safe to do so) to test this.
2. Blower Motor Resistor:
* The resistor is a common failure point: This component controls the different fan speeds. If it fails, the blower may not work at all, or only work on high speed (if at all). It's often located behind the glove box or under the dash. Accessing it can be tricky and may require some disassembly.
3. Blower Motor itself:
* The motor could be burned out: This is less likely if the fuses and resistor are good. Testing the motor directly with a multimeter requires disconnecting it, which can be more involved. If you're not comfortable with this, it's best to take it to a mechanic.
4. Wiring and Connections:
* Loose or corroded connections: Check all wiring connections to the blower motor, resistor, and relay. Corrosion can impede current flow.
* Broken wires: Inspect the wiring harness for any visible damage, especially where it might rub against metal parts.
5. Control Module/Switch:
* The blower motor control module: This is a less common failure point but is possible. It controls the signals to the motor. Replacing this is a more involved task.
* The HVAC control panel/switches: A problem with the control panel itself might prevent power from reaching the motor.
6. Other less likely issues:
* Low voltage: Though less frequent, consistently low voltage in your car's electrical system could cause the motor to fail to function.
Troubleshooting Steps:
1. Start with the fuses and relays – this is the quickest and easiest check.
2. If the fuses and relays are good, the blower motor resistor is the next most likely culprit.
3. If the resistor is okay, visual inspection of the wiring and connections is important.
4. Only if all the above steps have not resolved the issue, consider the blower motor itself, the control module, and the HVAC controls.
Important Note: Working on car electrical systems can be dangerous. If you're not comfortable with electrical work or unsure about any step, it's best to take your Bonneville to a qualified mechanic. Incorrectly working with car electronics can cause damage to your vehicle or even personal injury.
