Here's what's likely happening and what you should do:
* Worn-out blower motor bearings: This is the most common cause. The bearings are lubricated, but over time, this lubrication dries out, leading to friction, noise, and eventual failure.
* Possible other issues (less likely): While less probable given your description, a clogged air filter or debris in the blower motor housing could also contribute. However, these would usually cause reduced airflow at *all* speeds, not just at low speeds.
What you should do:
1. Check the air filter: It's a quick and easy check. A severely clogged filter can restrict airflow and put extra strain on the blower motor. Replace it if it's dirty.
2. Prepare to replace the blower motor: Given the symptoms, a new blower motor is the most likely solution. This isn't an exceptionally difficult job for someone mechanically inclined, but it does require some disassembly of the dashboard (usually under the glove box or console).
3. Consider professional help: If you're not comfortable working on your car, take it to a mechanic. Replacing a blower motor is relatively inexpensive compared to other car repairs.
Don't delay: Continuing to run the blower motor with bad bearings will likely lead to complete failure, leaving you with no heat or air conditioning.
In summary, the growling and inconsistent airflow at low speeds point strongly to a failing blower motor. Addressing the issue promptly is recommended.
