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    Blower Motor Repair

    My blower motor, much like everyone else's, was dying like a stuck Irish pig ("Did he sound anything like that!?")
    So instead of dropping the 200 for a new one I decided to try my hand at fixing it. Plus I heard it couldn't be done so naturally I had to try.

    It took me longer than expected to perform this job. I attempted to use a different bearing first and it didn’t work out too well. I will give some advice in parts that I would have done differently the second time around. Be prepared to take pictures of everything and I mean everything. This is not for the faint of heart. It is not an easy repair. If tinkering with beer makes you calm, have lots of it standing by.

    Go to McMaster.com and order the following parts.

    2 x Flanged Bearing 16mm OD for 8mm shaft x 5mm wide-
    http://www.mcmaster.com/mv1445545928/#catalog/7804K147

    6” 5/8”OD rod +.000 - .003 tolerance – This tolerance is important.
    http://www.mcmaster.com/mv1445545928/#catalog/8927K98

    JB Weld for added strength.
    http://www.mcmaster.com/mv1445545928/#catalog/7605A11

    It totals 24 bucks plush shipping.

    Then, obviously, remove the motor, don’t break it. Look somewhere else for those instructions.

    Take a red Sharpe marker and mark which blades have the little weights to balance the squirrel cages. You will need these cues when they fall off when you are hammering out the shaft. You may even want to remove them completely. It's up to you but don’t lose them or mix up how many and how heavy the weights are on each cage. They are tiny.


    Then get the assembly on your bench and start cleaning up the shaft ends on both sides with some Scotch Brite or I used 4 ot steel wool. If the ends are corroded it will be much harder to remove the cages.
    Measure the distance from the end of the shaft to the cage hub on each side. This will help when putting it back together.
    Spray a little WD40 or Silicone spray in the squirrel cage hub.

    I was looking at the assembly thinking there must be a way to take these cages off... The cages are suspended by 11 arches that meet in the center hub. We know these are very strong just based on their geometry so lets use that to our advantage.

    You need a way to suspend the whole assembly by the inner ring of one end of the squirrel cage. My vice rotated so I put some angle iron on both jaws and sat the inner ring on the angle iron. This gave me a pretty decent contact patch for the force to translate through as many arches as possible.

    The next step is similar to pulling a brake drum... Your going to have to hit it a lot harder than you think you should.
    STOP: Before you hit anything either keep an eye on the little weights on the squirrel cages or take them off. You do not want to lose these. If you take them off make sure you mark the blade that they live on. Take pictures!

    With the shaft clean and sprayed with a little WD40, set the assembly in the angle iron.
    I used a heavy hammer and started hitting the shaft lightly. I gradually worked up in force and it began to move. Take your time with this. Once it moves down and gets close to the hub get a punch and set it on the shaft to knock it through without hitting the hub.




    Repeat for the other squirrel cage. Make sure that the motor doesn't drop out the bottom though. Have someone there to catch it or rig something up.

    Set the cages aside. Are the weights still on the blades or did you lose them?
    Look for lost weights.
    Take hold of the motor and unbend the cages that hold the springs for the motor brushes. Don’t let them shoot into your eyeball. Put springs in bag and set aside. They will bounce and roll into the deepest darkest corner of the garage.

    The bearings are housed in the U shaped metal bracket on each side of the motor. You ONLY have to take one of the brackets off. I took the brush side off.
    The U bracket is held to the motor chassis by deformed metal tabs on the chassis. You'll need to put the motor in a vice and un-bend these tabs so that you can take what's left of the brush side bearing out. I unbent them with a hammer and a screwdriver. It was pretty easy. There are four tabs on each side of the bracket. Unbend them, do not break them or you will be forced to use the JB weld you just purchased, like me.


    With the tabs un-bent, pull off the U bracket. Be careful the brushes may be worn into the copper hub. Do not crack them.

    Knock out the inner race of the bearing with a socket and extension and a hammer. You know why these bearings fail? Because they are oiled felt bearings. No balls, friends, no balls.


    My bearings had quite an eccentric slot worn into them. It’s a good thing the shaft is harder than the bearings.
    Once the inner race is out, pull out the felt and cage with needle nose pliers.

    You can toss these along with the inner race; you wont need them any more.
    Set this U bracket aside for now.

    Next take the e-clip off of the motor shaft on the other side of the motor chassis. There is a stack up of washers that will pull off when you pull the shaft and coils out of the housing. Keep track of these you might need them.

    Perform the same operation and knock out the inner race and take out the bearing felt and cage.

    When you get your parts in from McMaster first de-burr the 5/8” shaft ends or file them down. Here is why we want the shaft tolerances the way we do:
    The hole in the U brackets for the shaft is about .608” in diameter.
    16mm = .630 inches. If the .625” shaft were to have a +.005 -.005 tolerance, which is common, we could potentially ruin our press fit for the bearing that we are looing for if the shaft were at the upper limit of it’s tolerance.
    The part number given has tolerances of +.000 - .003”, and nominal dimensions we would have .005” interference for the press fit which is on the upper limit but for the DIY’er it’s a pretty good fit. A .008” interference may be too much, but again, better than the potential .010” interference with the other shaft. A tapered pin would also work to flare the hole. I couldn’t find one that would work though.
    Set the U bracket that is attached to the Chassis down so that the shaft has to pass through the magnets before hitting the U bracket - U bracket on bottom, Chassis on top. Put the 6” shaft through the magnetic field and seat it in the flared hole.
    Drive it through the shaft hole with a hammer to flare the hole. Use your discretion on how far to go. I only drove it through about an inch before knocking it back out.

    Do the same on the Brush U bracket.

    Now press the flanged bearings from the out side in. The flange should sit on the edge of the flare when completely seated.
    I used a socket on the inside of the U and put the bearing on the outside, then I pressed them together in the vise. The bearing flange will sit flush with the U bracket hole.


    Once the bearings are pressed in, reassemble the system. You will probably have to remove the washers that were behind the e clip due to the added height of the flange bearing.

    Make sure the shaft spins without the coils hitting the magnets.

    Seating the Brush U bracket is tricky. You will have to re-deform the metal to get it to hold. If you find yourself chipping the soft aluminum off, apply JB weld to the area and clamp for the night.

    Put the springs to the brushes back in back in place and test the motor in the car before reinstalling the cages.

    If it works knock the cages back onto the shaft and make sure the distances you measured earlier are the same.


    Then have fun reinstalling it in the car without breaking it!

    Finally, enjoy your new, quite running blower motor for the price of a six pack and some McMaster parts.

    #2
    Do you happen to have any pictures?
    1991 318is ---230K - DD
    1991 318i ---- 308K - retired

    Originally posted by RickSloan
    so if you didnt get it like that did you glue fuzzy oil to the entire thing?
    sigpic

    Comment


      #3
      Originally posted by jrobie79 View Post
      Do you happen to have any pictures?
      I had pictures linked to the write up. After reading it again, it is not that useful without pictures. I will try to hunt them down. If I can insert them into the post I will. I think they had to be hosted before, which would be why they are no longer there.

      Comment


        #4
        Sorry, but the market is filled with aftermarket alternatives for under $50 brand new. At that price, it's not worth the trouble. Furthermore, the plastic squirrel cages get extremely fatigued over time. I would not reuse them. I recently had one come apart during regular usage. It'd be a shame to do all that work and shortly after have the cage come apart. There's also brush/commutator wear that occurs that should be addressed. With a new drop in unit, you get all new components in a balanced assembly, ready to go.
        Last edited by reelizmpro; 11-17-2020, 12:20 PM.
        "I'd probably take the E30 M3 in this case just because I love that little car, and how tanky that inline 6 is." - thecj

        85 323i M TECH 1 S52 - ALPINEWEISS/SCHWARZE
        88 M3 - LACHSSILBER/SCHWARZE
        89 M3 - ALPINEWEISS II/M TECH CLOTH-ALCANTARA
        91 M TECHNIC CABRIO TURBO - MACAOBLAU/M TECH CLOTH-LEATHER

        Comment


          #5
          Originally posted by reelizmpro View Post
          Sorry, but the market is filled with aftermarket alternatives for under $50 brand new. At that price, it's not worth the trouble. Furthermore, the plastic squirrel cages get extremely fatigued over time. I would not reuse them. I recently had one come apart during regular usage. It'd be a shame to do all that work and shortly after have the cage come apart.
          where are these fans under $50?
          1991 318is ---230K - DD
          1991 318i ---- 308K - retired

          Originally posted by RickSloan
          so if you didnt get it like that did you glue fuzzy oil to the entire thing?
          sigpic

          Comment


            #6
            Originally posted by jrobie79 View Post

            where are these fans under $50?
            https://www.ebay.com/itm/New-Blower-...3/283089116913

            Comment


              #7
              Quite a few alternatives on Amazon as well. Apparently the Z3 uses the same blower style so that's another option if you want OEM. Mine is from Amazon made by "ZM" and the quality is good. Time well tell how good but I decided to give it a shot.
              Last edited by reelizmpro; 11-17-2020, 12:22 PM.
              "I'd probably take the E30 M3 in this case just because I love that little car, and how tanky that inline 6 is." - thecj

              85 323i M TECH 1 S52 - ALPINEWEISS/SCHWARZE
              88 M3 - LACHSSILBER/SCHWARZE
              89 M3 - ALPINEWEISS II/M TECH CLOTH-ALCANTARA
              91 M TECHNIC CABRIO TURBO - MACAOBLAU/M TECH CLOTH-LEATHER

              Comment


                #8
                I concur with Reelizmpro, I bought a blower assembly from Amazon for around $60 and its been working well for over a year and I use the car almost every day.
                Owner - Bavarian Restoration
                BMW and European Electronics Repair and Restoration
                www.BavRest.com
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                Comment


                  #9
                  I already took the cages off and ordered the parts before I realized they were so cheap, oh well. So if the pictures end up popping back up in gonna give it a go. Worst comes to worst I'm out a couple hours and $80 🤷🏼‍♂️
                  1991 318is ---230K - DD
                  1991 318i ---- 308K - retired

                  Originally posted by RickSloan
                  so if you didnt get it like that did you glue fuzzy oil to the entire thing?
                  sigpic

                  Comment


                    #10
                    Duplicate post
                    1991 318is ---230K - DD
                    1991 318i ---- 308K - retired

                    Originally posted by RickSloan
                    so if you didnt get it like that did you glue fuzzy oil to the entire thing?
                    sigpic

                    Comment

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