Here are more likely causes:
* Blower Motor Resistor: This is the most common cause of this type of problem. The resistor controls the different fan speeds. If it's failing, it might allow lower speeds to work but not the higher ones.
* Wiring/Connections: A loose connection, corroded wire, or broken wire in the blower motor circuit could interrupt the higher speed signals.
* Blower Motor Itself: While less likely if the lower speeds work, a failing blower motor could still be a contributing factor. It might struggle to reach the higher speeds due to internal wear.
* Fuse (less likely): A blown fuse would typically result in a complete lack of blower motor function. However, it's worth checking nonetheless.
Troubleshooting Steps:
1. Check the fuses: Locate the blower motor fuse in your fuse box (usually under the hood or in the cabin) and inspect it for continuity.
2. Locate the blower motor resistor: This is often found behind the glove box or under the dashboard. Access it and visually inspect it for any signs of burning or damage. (A replacement is relatively inexpensive and easy to install).
3. Inspect wiring: Trace the wiring from the blower motor resistor to the blower motor and check for any visible damage, loose connections, or corrosion.
4. Test the blower motor (if you're comfortable doing so): This involves applying direct power to the motor (with the proper voltage) to see if it works. If it does, the problem is likely before it (resistor, wiring, etc.). If not, the motor needs replacement.
Before you start replacing parts: Check online forums and repair manuals specific to your 2000 Silverado. There might be detailed troubleshooting guides or known issues for this particular model year. You can often find diagrams showing the wiring and location of components. Replacing the wrong part will cost you time and money.
