How to Clean the A/C Blower Instead of Replacing

Intermittently, the A/C blower has been going out in my wife's 2007 Prius. She's been banging on the dashboard in front of the passenger seat to get it blowing again. Everyone in the family has their favorite area to get it started and theory for why their area works better than others. Because of the intermittency, I suspected something was getting dirty, worn, or both

So, I decided to fix this one way or another. Reading threads here on Priuschat and viewing Youtube videos, I decided I'd try to fix the problem by cleaning the actual DC motor and possibly replacing the carbon brushes rather than paying the $40 - $110 for a new blower assembly. My hypothesis was that either debris was getting into the blower area (our driveway is shaded by Live Oak trees that shed their leaves twice a year and have all kinds of little bits that can jam their way into tight areas); or the motor brushes were wearing; or the motor was dirty; or all three.

When I removed the blower assembly, there was no debris, so I knew it was the motor. Either the brushes or dirt/grime. I ended up NOT being able to replace the carbon brushes, but I did clean the DC motor with electronics cleaner and made sure the brushes were seated as far in as they could go. The end result is that the air now blows just fine all the time and I didn't have to buy a new assembly.

So, here's how you can clean your A/C blower motor instead of replace it:

First, buy electronic cleaner, either at an automotive store, Radio Shack, Amazon, or your favorite electronics tinkerer store.



Next, take out the A/C blower assembly. This is what the assembly looks like from the fan side. Note that you'll have to take off the hose clamp looking thing on the spindle. Very easy to do with pliers.



This is what the under side looks like, which is where the motor is attached to the frame.



Unscrew the two screws in the photo above so that the motor is no longer fastened to the plastic frame. Also be sure to take off the hose clamp thingy on the spindle.

The question became, how to separate the fan from the motor? At first, it wasn't obvious to me. I couldn't put a puller on the blower cage because it was plastic. So, I grabbed the fan with a vice grip that was closed "just enough" to grab it but not squish the plastic to the point of deforming it. I pulled and the blower cage separated from the black frame. However, it did not separate from the motor. Still, progress, and a pleasant surprise that it worked. I was on to something.



Next, I needed to pry the blower cage off of the motor's spindle. I hit upon the idea of using a pry bar because it seemed like it had the right angle to it. I placed it so that the tip was between the blower cage and the motor's spindle. Instead of prying, I twisted so that the tip of the pry bar acted as a wedge that pushed the blower cage up. Once I got it started moving, I could wiggle it with the help of the pry bar until it came off. I you don't have a pry bar, you may be able to use a large flathead screw driver. Maybe. Either way, don't go crazy on it because you don't want to break or permanently deform the plastic. Prybars are relatively inexpensive at auto stores.



Now that the blower cage is off, you can see the motor by itself:


Because it was full of gunk, I was hopeful that my hypotheses was true: that it was the dirt and grime that was causing the intermittency. The more the dirt and grime built up, the more we had to bang on the dashboard to get the brushes to make an electrical connection.

Next, I pried the cap off the top of the motor using a flathead screwdriver, again as wedge. Stick a flat head screw driver at the bottom of the cap and twist it. Doing this as you work your way around the cap makes it easy to take the cap off. I don't think it'd be a big deal if you couldn't get the cap off, though.

You can see a clip on the right side of the motor in the above photo. This is a retaining clip for a brush. There are two, 180 degrees from each other. You can take the clip off and a spring will pop out. This spring holds the carbon brush against the spindle, or more accurately, the stator. Carbon brushes are soft, you can easily gouge them with something pointy. Because they're physically contacting the rotating spindle, they wear. Some of that gunk is carbon powder, rubbed off through time. The brushes are connected to a braided wire. I couldn't figure out how to open the motor further to remove the brushes, so I decided to just spray the whole motor inside and out liberally with electronics cleaner and then let it dry. Wipe off the grime with paper towels.

If anyone else knows how to open up the motor to replace the brushes, please reply to this thread. Also, I'm not sure exactly where I would get new brushes (maybe a good hardware store), but I have seen replacement brushes in cheap, cordless drills I've purchased. So if anyone has a good idea where to buy new brushes, please reply to this thread. They can't be that expensive.

Also, because I wasn't able to open the motor further, I don't know how/where the braided wire from the brush is attached. I'm assuming it's either clamped by a screw or soldered.

I ended up popping off the clamp, taking out the spring, and pressing the brush against the stator with a screwdriver so that, 1) knew that it was seated as far as it could go (it dragged against the stator as I turned it by hand), and 2) I could get a sense for the amount of brush material left. I think there was plenty to last for another 3-5 years.

Once the motor was clean and dry, I reassembled in reverse order. Everything went back together quickly. The only trick is to make sure you line up the slots in the plastic frame with the copper blades set at right angles to each other.


Press the frame into the motor and screw the two screws in the back of the frame which fasten the frame to the motor. Then, press the blower cage back onto the motor spindle; it only goes on one way. Use pliers to put the clamp back onto the nose of the blower cage and you're ready to install the assembly back into your Prius.

If you have a 12V power supply, you can power up the blower assembly before and after you clean as proof that the cleaning worked. If not, reinstall and test it by turning on the A/C.

These are heavy duty motors, bigger than the Speed 400 or Speed 500 Mabuchi motors you see in all kinds of battery operated power tools. It seems a shame and a waste to just throw them out when sometimes all they need is a little cleaning.

 

Ah! Rotor vs Stator! Thanks for clarifying.

What a great tip about carbon building up between the commutator segments and causing a short. Do you know what code the Prius would throw if that happened? I'm sure it'll help people diagnose their problem.

 

I use the one from Autozone, or maybe O'Reilly's. Maybe it's a Fram. I tend to buy the cheapest one. I think I'm changing it once a year. But...like I do with engine air filters, I hold it up to the sun and if it shines through the pleats, it's still good so I reuse it. I learned this as a teenager so I can't say if it's still a valid thing to do.

Note that the blower pushes air through the filter; I'm not sure where it sucks from, but wherever that is, that's where the dirt came from that I cleaned out of the motor...and, of course, the carbon dust from the brushes.

 

Doh! My mistake.

The blades were dirty as well, so I cleaned them. The blower cage was also dirty, on the underside, you can see the dirt clearly in the picture with the pry bar. It was clean on top (the first picture). This may give us a clue to where the dirt came from.

The blower spins horizontally. The blower's vacuum, then, causes air to flow from the cabin through the cabin filter, and into the blower cage. I then gets blown out through some orifice leading to the vents. This orifice must be somewhere near the cage. The air flow is down through the cabin filter, then sidewise out the orifice.

The assembly and motor are not in an airtight box, so I assume there's some vacuum on the underside of the fan as well. My hypothesis is that this vacuum is what caused the dirt to enter the motor and the underside of the cage. Because passenger's feet are directly under the blower assembly, it's reasonable to assume dust they bring into the car ends up in the motor.

Which means....all Prius blower motors will have this crud on it (especially ones dusty climates) as they get older.

 

Here's my thinking: if particles were coming around the seal on the cabin filter, then the top of the cage would be dirty. Mine wasn't. It was clean as a whistle. I interpret this as the cabin filter doing it's job. The underside of the cage was dirty, as were the blades. This is the side that faces the motor, which was dirty as well. This is why I think there is some minor vacuum there, drawing dirt particles in.

FSM isn't is going to tell me where the problem lies. Evidence does. At this point, >how< the motor and cage got dirty is more of a curiosity. The main point is that the problem's solved without having to spend money on a new assembly. The air comes out of the vents stronger than the day we bought it with 40,000 miles. On to the next problem to solve...