1. Fuses and Relays:
* Locate the fuse box(es): Your Trailblazer likely has an under-hood fuse box and one inside the cabin (often under the dash). Consult your owner's manual for their exact locations and fuse diagrams.
* Check the blower motor fuse: This fuse is usually clearly labeled (often "blower motor" or similar). Visually inspect it for a blown filament. Replace it with a fuse of the same amperage if blown.
* Check the blower motor relay: The relay is an electromagnetic switch that activates the motor. It might be in the same fuse box or a separate one. You can often swap it with a similar-looking relay (same amperage and type) to test if it's faulty. A clicking sound when you switch on the fan suggests a problem with the relay itself. A silent relay points to an issue elsewhere in the circuit.
2. Blower Motor Resistor:
* Location: The blower motor resistor is a common failure point. It controls the fan speeds. Its location varies slightly depending on your specific Trailblazer model, but it's often under the dash, near the blower motor itself. You'll likely need to remove some trim panels to access it.
* Testing: While a visual inspection can sometimes reveal a burnt resistor, the most reliable way is to test it with a multimeter for continuity. If the resistor is bad, it will need replacing.
3. Blower Motor Switch:
* Testing: This is the switch you use to control fan speed. It's tricky to test directly without specialized tools, but you can try testing the wiring going *to* and *from* the switch. Check for power and ground at the connections. If the switch is faulty, it'll need replacement.
4. Wiring and Connections:
* Visual Inspection: Carefully inspect all the wiring related to the blower motor, including the connectors. Look for any signs of damage, such as frayed wires, corrosion, or loose connections. Pay close attention to the connections at the blower motor itself, the resistor, the switch, and the fuse box. Repair or replace any damaged wiring as needed.
5. Blower Motor Itself:
* Testing (Advanced): This is the least likely culprit unless you've already checked everything else. You would need to test the blower motor directly with power to confirm it's working correctly. This usually requires removing the blower motor (often under the dash, sometimes involved).
Important Notes:
* Safety First: Disconnect the negative battery terminal before working with electrical components.
* Owner's Manual: Your owner's manual provides crucial information about your specific Trailblazer's fuse box layout, and often includes troubleshooting tips.
* Professional Help: If you're not comfortable working with car electrical systems, it's best to take your Trailblazer to a qualified mechanic.
By following these steps systematically, you should be able to pinpoint the cause of the problem and get your blower motor working again. Remember to check your fuses and relays first, as they are the easiest and cheapest components to replace.
