Other, less likely possibilities include:
* Faulty blower motor control module: This module receives signals from the climate control system and sends the appropriate signals to the blower motor. A fault here could limit functionality.
* Wiring issues: A short, break, or poor connection in the wiring harness leading to the blower motor or resistor could cause this.
* Blower motor failure (less likely): While less common, a failing blower motor itself *could* exhibit this symptom, though usually it would manifest as a complete failure rather than just a speed limitation.
In short: The blower motor resistor is the most probable culprit, and it's relatively inexpensive and straightforward to replace. A qualified mechanic or experienced DIYer can diagnose and fix this issue.
