So, long story short, I replaced my 240's blower motor about 3 years ago with a SIEMENS part, and since last winter, it has been screaming, rattling and all, the vibration it generates even shakes the steering wheel! So I decided to dig it out and see what's going on. And here is what is looks like. Not only it has large amount of shaft play, but the internals looks dirty and rusty. the winding looks burnt more or less. The open casing design really isn't the best idea in a car without a filter. So, instead of buying another one of these and bet on it, I digged out the original motor that I took out 3 years ago.

 

Took it apart was not diffcult job, and immediatly I start to see how the original motor is so much better designed than the newer one (I will explain later) and decided to rebuild it.


My motor has a sized bearing, which took bit of knock to take off. These motors use bushing style bearings, there are no roller or ball, they need to be greased and the main reason for failing is dried up grease. The stuck bearing was capped in the case end behind the brush assembly. There is quite some space for the bearing to move around and hold grease.


This is one end of the motor, where the brushes are, the center cap that holds the bearing is removed and old grease cleaned.


This is the stuck bearing on the shaft, the ball shaped metal thing is the bearing, behind is a spring and a grease cap that are not suppose to come out with the shaft.


The bearing too quite some twist to free up, but eventually it came loose.


I cleaned up the shaft and the brush contact, not perfect but I think won't make much difference in thie particular motor. Notice the little white plastic piece above the brush contact, do not lose it. The 4 grooves on the shaft from what I guess, is to help prevent grease spin out of the grease cap (At lease when I tested it, the grease stopped there )

Re-pack the bearing housing with grease, I used high temperature wheel bearing grease, and put the bearing back in, the bearing will be pressed on the housing with that little spring, and tap the grease cap into the housing, the housing edge is slightly tapered, it should fit snug. This design actually gives the bearing some freedom to turn in any directions without experience excessive pressure on one side (The spring will hold it in place), which should make it last longer in high vibration, movement environment (like in a moving car). The SIEMENS motor I bought lookes like a press in bearing with not much flexibility.

Lube the shaft end with grease and push it in, after assemle the brush it should look like this. Of course, clean the rotor before do it, I even brushed little bit of brake caliper paint on the armature (probably not supposed to do, but probably wont hurt as well). The shaft should turn freely but the bearing is NOT suppose to turn. If the bearing turn with the shaft, you will hear lots of noise and the spring bumping inside, it means the bearing is deformed. In that case you can try to re-shape it, polish the shaft bit, or, ideally, replace the bearing. In my case the bearing was quite smooth and the shaft was free to turn. If there are play between the shaft and bearing, the bearing is too worn, in that case, replacing the bearing is the only way. (Or you can machine your own bearing).

In ideal case, the brush should also been replaced, but mine still has decent amount left and this is a one afternoon job, so I left as it is.



Also clean the magnet, I added a light coating of brake caliper coating on it as well.



This is the other side cap, at the center you can see the grease cap in place, it is the same design as the brush side, the bearing is pressed against the cap by a spring. You can pop the cap to re-pack grease, I used a large syringe to inject between the gap. Lube the shaft and put it in.

Once you screw on both end caps, you will found that they actually formed a sealed motor assembly, this is the inner assembly of the motor, the core. Because of this sealed design, it blocks off most of the dirt and mouister from the rotor. This is much better than the later SIEMENS open casing design.



Now it's a good time to prepare the outer housing. I sprayed them with braker caliper paint as well for prevention. This is the housing that actually mounts to the car and holds the inner assembly inside.



Put on the rubber bushing on the inner assembly, There is a big one for the end with wiring, a smaller one on the other end. (They only goes on one way, so pretty hard to do it wrong). In the piture I only showed with a cap, but in reality you should have the inner assembly as a whole part right now. I also added some dielectric grease on the bushing. Notice the holes on the small bushing and the bumps on the larger bushing? They are designed to absorb vibration! With these two bushings, the inner motor has no contact with the outer housing, it is suspended inside the housing, so you have minimum vibration and noise transfered to the car. Very good design! The SIEMENS motor is a solid piece, so you will feel everything!

Also, by this design, the outter housing should have no electrical connection at all, test the shaft and the outter housing with a voltmeter, they should have no contact.


Re-assemble is very easy, I broke all the tabs unfortuanly, but the motor will be held by screws on the car, so it really doesn't matter. I also used some gasket maker to seal the outter housing so it's easier to put in as one piece. I added some gasket maker around where the housing contacts the car as well, to further reduce the vibration transfer (not the best looking job and not necessary, it can be done better by cutting a thin rubber sheet )

On the wire end of the motor, there is a wood looking piece snug on the shaft groove with a metal plate on the outside, that is screwed on the motor. Make sure you install the motor in your car first, while the motor is running, slightly adjust the screw, this wood piece is designed to position the rotor, so it is at the right position, over the years, the wood piece will be slightly worn, you just need to tighten it a little bit, but I found it is better to adjust it while the motor is running (you can supply power to it outside the car as well). Because only when the motor is running, you will be able to hear the noise change. too tight or too loose will make the motor nosier, you know the best spot is reached when the motor all of suddent goes silent. With this design, the rotor shaft will be locked at best position and there should be no play in the shaft, so when you turning hard, the shaft won't drift because of momentum. (My SIEMENS motor scream whenever I turn hard left).

One thing I couldn't figure out is, there is a hole one end of the outer housing, which in this case I covered it with some metal mesh. Not really sure what is the purpose of this hole. I tried to suck on it, the outer housing is not sealed, I can draw air from around the rubber bushing. (My guess is when the motor is running, because it sits at the center of the air box where the fan blades are on each side, if one side has slightly different air pressure, a small amount of air flow can be drawn through the outer housing, and because the inner motor assembly is suspended inside, the air flow can help cool the motor assembly (if that's ture that will be cool, but i can't see how this helps during winter when the heater is on))

This is the sound of 3 years old SIEMENS motor:
https://drive.google.com/file/d/1Pax...ew?usp=sharing

This is the sound of rebuilt, 30 years motor:

https://drive.google.com/file/d/10Rn...ew?usp=sharing


Both at speed 2. Now at setting 1, when engine is off, and night in the garage, I hear very little sound from the motor. setting 2, I hear whoooshhhh sound of the air flow, but not much noticbale when car is moving and radio is on. Setting 3, lots of air noise, and slight motor sound, just like any DC motor at speed. setting 4 is mega loud air noise and motor whine (the healthy whine of a brushed motor)

Noise test in the car: https://drive.google.com/file/d/1uXm...ew?usp=sharing

Maybe I'm just unlucky with the new motor, but for anyone that's having an old motor laying around, I really think the original motor worth a rebuild and can last lot longer than the newer one.