Here's a page I threw together in a few minutes to illustrate replacing the W124 blower motor. This is intended for do-it-yourselfers of average skill like myself.
I'm not a professional mechanic, just a do-it-yourselfer. This article probably has some of the steps out of order, omitted, or performed incorrectly. All I know is it worked for me. If it works for you too, great! If not, I cannot be held responsible. PROCEED AT YOUR OWN RISK.
My particular car is a 1990 300CE with the Behr air conditioning unit. I ordered the bare replacement motor ($99.00 without squirrel cages) and it dropped right in. I've read posts by W124 owners who have had assorted problems installing aftermarket replacement motors. So as the saying goes, your mileage may vary. I strongly recommend doing some research before you jump into doing this job. If you decide to go for it, proceed with caution. If in doubt, STOP and consult an expert and/or a shop manual. I strongly recommend purchasing the CD-ROM-based Mercedes shop manual as I found it quite helpful while performing this repair.
Moving right along...
First, remove the wiper arm from the wiper assembly. This lessens the chance of cracking the windshield and makes it easier to get the wiper motor assembly out. For that matter, I'm not sure you could get it out with the arm attached. Just trust me on this one. :-)
Raise the wiper arm until it is fully extended. Remove the trim piece covering the set screw.
Remove the allen head set screw, then slide the arm off the shaft. As you can see in the photo, you may want to use a screwdriver to relieve enough tension for the arm to slide off.
Next, raise the hood and remove the two plastic trim pieces that cover the lower edge of the windshield. They're held in by spring clips and should only require a firm tug straight out.
Now remove the eight screws along the bottom of the windshield (see crude-but-effective red arrows). Note that the outer two are not visible in this photo. Also remove the four tiny screws securing the rubber seal surrounding the wiper motor assembly. This also would be a good time to pull the weather stripping out of the way.
The outer plastic trim sections are joined to the center section with these white clips - one on each side of the car. Pull them straight out toward the front of the car, then separate the pieces. Be careful not to let them get away from you and fall into the car's nether regions! I also removed the plastic piece behind the battery that covers the ECM, but this may not have been necessary.
Next remove the foam-covered trim directly behind the cam cover. There are two large, plastic thumscrews securing it to the front of the box containing the blower motor. Hopefully the trim in your car is in better shape than mine. This photo also shows a decent view of the weather strips that have to be partially removed during disassembly.
Remove the front part of the grille by releasing the two tabs on the outer edges that connect it to the adjacent trim panels.
Remove two screws that fasten the grille to the top of the box, then carefully remove the grille.
Now the wiper assembly is accessible. Remove the four 10-millimeter nuts and then carefully lift the assembly out of the car.
Okay, I didn't take any photos of removing the top of the box from the blower motor. It's very straightforward - just pop the clips loose and carefully remove the top of the box. To remove the motor, unclip the metal strap from its fastening point in the back, then remove the two wires from their terminals. BE CAREFUL
removing the motor assembly! The squirrel cages are fairly delicate. If you mess these up, you're looking at a $300.00 fan assembly instead of a $100.00 bare motor.
To ensure proper balance, mark the squirrel cages before removing them so that they can be installed on the new motor in their original alignment. While it might not make a difference, I was careful to put the cages on the same side of the new motor as they were the original motor, then rotated the two fans into their original alignment using my marks. Proper balance is important or your motor could wear out prematurely.
The most tricky part of the job is removing the squirrel cages from the old motor. My friendly neighborhood Auto Zone was kind enough to lend me this gear puller for a mere $40.00 deposit. There may be a better way to remove the squirrel cages, but this was the safest I could think of. The key here is patience. Work slowly! Like I said before, it's going to cost you a fortune if these babies get broken. I used a little WD-40 to help move things along. If you do the same, be sure to clean off all the WD-40 before you put them on the new motor. The squirrel cages will slide onto the spindle of the new motor fairly easily. I wrapped a rag around one end of the shaft and clamped it in some vise grips to hold it still. Then I pressed the squirrel cage onto the opposite end of the shaft and twisted back-and-forth until it was close to the correct position.
Note that the squirrel cages must be located in the proper position along the length of the spindle in order to clear the sides of the box. It took me three or four test fittings to get everything tweaked just right. Make sure the motor fits securely into the mounting bracket and check to make sure the squirrel cages rotate without interference. Once everything looks good, fasten the motor with the metal band, plug in the power connectors, and put the top back on the box. Turn on the ignition switch, select the "normal" climate control setting, and select high fan speed. If you get strong airflow to the correct vents, congratulations! Now you can finish the reassembly.
If you hear the fan but there is little or no airflow, check to make sure you don't have the squirrel cages facing the wrong direction.
Please Email any questions, corrections, or additions to Jay Slabotsky at firstname.lastname@example.org.
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Jslabotsky wrote a post before, entitled W124 Blower Motor Removal Photos
. Only problem was, there were no photos...the link was dead.
I just did mine about 8 weeks ago, prior to knowing about this forum, therefore I’m short on photos for you. Also, sorry if I miss any steps, one of my pet peeves, but it’s been 8 weeks ago.
Here we go….
You’ll need: Just basic tools (Phillips screwdriver), and a magnetic antenna picker upper. You might also need one of those long grabber things as well. You’ll be doing a lot of far reach leaning over the car’s fender. Either use a fender protector, or empty your pockets of keys, turn your belt buckle to the side, and make sure your zipper is covered by a long shirt to help protect the car.
Have your new parts ready. If you buy new, see if you can return if the part is not needed. Your regulator might be fine, the blower fan might just need some oil. You won’t know until you get there. If you buy used parts, you can try your replacement fan and regulator without taking any of the parts off, instructions below.
is to take photos, hopefully with a digital camera, as you go. Putting this all back together again, is a bear. Unless you’re a very competent mechanic, you’ll need photos to remember what went where.
, I don’t know if it’s necessary, but you may want to disconnect the battery.
Take off the window trim at the bottom of the window. I found out, at the end of the job, that the window trim comes off easily. It caused me a lot of problems lifting that rubber up trying to get bolts off, so I just saved you about 2 hours of work. Just pull it from the end closest to the wiper assembly, at the same angle it currently is, towards you, and it pops right out; take off silver trim underneath, and the rubber trim around the windshield wiper. Take pictures or draw how it’s layed out. Take out the water gulleys and other trim shown in the photo. There are 2 or 3 knob kind of things on the front side of the wall. From memory, these will have to be removed as well.
Once all the trim is gone, you can get to the wiper assembly. Note that on your model
(mine’s a ’91 300d) you probably have 2 screw slots and 4 holes, yet only 2 screws holding it in. I just saved you another hour trying to figure out where your screws went when you replace everything. Note how the center bracket is positioned on top of the firewall bracket. Work the entire wiper assembly out of the car.
Now you’ll see a black plastic box of sorts, under the wiper assembly area, about 12” long. The fan is enclosed in this box. I recommend that you put something around the lower half of this area to catch clips and screws you will lose, then if you need to get to your regulator which is below that, lower your catch system at that time. I used some crumpled up newspaper. If you do lose anything on the OUTSIDE of the metal tub area, that is just a drain area, it might come out under the car. If you lose something down INSIDE the metal tub area, you need to get that out. Much better than chasing things down in there with the magnetic antenna, as they’re very hard to get. I just saved you another hour.
With the fan exposed, you’ll see that there’s a large, 1 ½” wide brass spring clip over the top of the motor. Take a magic marker, and mark across the fan clip and motor. In case you re-use this fan, you’ll know about where it will have to go back. Also, take a photo of the area at this point, you’ll thank me later. Disconnect the red and blue wires, making careful note of how and where they came out and ran to get there.
The fan clip comes off by putting a flathead screwdriver or other tool onto the far side of the clip (toward the cabin of the car), and pushing down and forward on the clip end. It sort of springs down and out. Once that’s off, you can pretty much lift the fan straight out. Be careful not to break the squirrel fan. If you can get the squirrel cage off each end without breaking it, you can use that on a new motor for just $140 vs. $350 with squirrel cage.
From here, you can try your existing fan to see if it works. First, give the fan a spin by hand to see if it will even turn. The fan might be locked up. It should turn semi-freely by hand. If it’s reluctant to turn, oil it where needed, see if you can get it to turn freely.
If your fan is moving freely, follow the plastic coated line from the regulator (which is under the blower fan area), and see that it goes up to the brake fluid reservoir area. (See photo).
Disconnect your existing regulator by squeezing at the sides toward the top. If you’re squeezing the sides too low, your hand is preventing the squeeze clips from from coming out. Hook up the new regulator to the old fan. Set the a/c fan control inside the car to O (off).
Connect the battery and get someone in the car. Hold the fan firmly in your hand at the center. Give it a spin by hand to make sure it’s not catching on your long sleeve shirt or anything. Turn the key to one stop prior to turning the engine on so you know you have power to the fan. Have your co-worker turn the fan on. If the fan doesn’t work, have them play with some of the buttons, high/low and different a/c controls. If you’re lucky, you’re fan will work, blowing nice and smooth. Try high and low.
If the fan didn’t work, it may be your regulator, or that the fan just needs oiled or needs new brushes. The brushes are the tiny area inside the fan motor, a little caged area, holding down what looks like a pencil eraser, being held down with a spring. Hopefully you have at least ½” of the brush left. I’d read previously, you can get new brushes fashioned at any electrical motor repair place; vacuum places, etc. You might get lucky and get them for just $3 or so. Better than buying a new fan motor!
If you need to replace the regulator, that is yet twice the fun to replace. There’s a radiator type thing (heater core?) to the back of the regulator, toward the cabin. While working with the regulator, be careful not to damage that. There’s only one way for the regulator to come out, and it’s not easy.
You have to take off the 3 triangular screw pattern black plastic fan holder off. With that off, you’ll see a concave black plastic sheet that covers the regulator. Unscrew 2 screws holding the regulator down, and work the regulator to the opposite side of the pins; toward the driver’s side of the car. Once that’s out, disconnect the cable at the opposite end and work that out. Note how and where the cable and other wires run. With the regulator out, clean up whatever loose foam there is down by the radiator thing. I used a vacuum with a hose extension piece. There’s also a flap with sound deadening foam on it. Pick off any pieces that are obviously due to fall off and leave the rest.
To install the new regulator, first see where the 2 screws are on your old regulator. The new regulator probably has a foam going over the area, obscuring the holes. Poke with something sharp to locate the screw holes and to move away the foam from that area. You might also want to take a red magic marker to mark the holes to help you see them better when you put the regulator in place. Put the new regulator in the same way the old one came out. The problem I had, was that my new regulator holes, even though drilled in the same spots as the old one, wouldn’t match up with the screw holes in the black plastic. I tried, and tried, and tried, for two hours one day, then my neighbor and I tried for 2 hours the next. Couldn’t get it; the holes were nearly ½” apart! I finally drilled 2 new holes in the black plastic so I could get the screws in it.
Once that was done, I put everything back together again. I ran into a problem with the windshield wiper assembly; the bracket of the assembly wouldn’t go in above, or under, the bracket mounted onto the firewall. It just wouldn’t fit back in right. After much struggling, I found out that the 2 brackets just sort of sit on top of each other. Even though I hadn’t taken the firewall bracket off, I had to in order to get everything to match up properly.
Sing praises to me if this has at least reduced your work time.
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