If the blower motor for your Chevy S-10 Blazer (or similar SUV) makes a gravely or grinding noise when you turn on the heater or air conditioner, then its internal bearings are failing. Since the noise isn't going to ever improve and the blower motor will eventually give up and stop working altogether, the only fix for this problem is to replace it with a new one.
Replacing a blower motor is a simple procedure that anyone with a few basic automotive repair skills can do in less than an hour. If you decide you want to tackle this relatively simple auto repair, then follow each of these steps to do so successfully:
Step 1: Remove the Power Control Module
To gain access to the blower motor, first you need to remove the power control module (PCM). To do so, remove both blue cable locks. Once removed, depress the tabs on the cable connectors and remove the top two cables. Once the cables are out of the way, remove the two bolts holding the PCM in place. Slide out the PCM and remove the two lower cables now that they are easier to reach.
Step 2: Remove the Radiator's Overflow Reservoir
There will be three bolts you need to remove to get out the overflow reservoir for the radiator. Remove each bolt and then carefully lift out the reservoir. To fully remove it from the engine compartment, you will need to disconnect the radiator overflow hose.
Step 3: Remove the Old Blower Motor on the Firewall
The blower motor is located on the firewall on the passenger side. It has an electrical connection that you need to remove. Once you have removed the wires, then you need to cut the firewall material covering the old blower motor. Trace around it with a sharp razor knife, taking care not to push down too hard. Peel back the firewall material to expose the bolts holding the blower motor in place. Remove the bolts and pull out the failed part.
Step 4: Put in the New Blower Motor
Before putting the new blower motor in, make sure it matches the old one. As long as it looks right, then install it by reversing each step above. Put the new motor in place, bolt it in, and reconnect the electrical wires. Use a product like Permatex to reattach the firewall material where you cut it away.
Once the new motor is in place, then replace the radiator's overflow and put the PCM back in place. Once all the connections are made, then your new blower motor should work and the loud, annoying noises will be gone.
Contact an auto repair shop in your area for additional advice.