So of course I was driving home one a smoking hot day and my blower quits. Black on black land yacht stuck in traffic with no air. When I got home I did some research and as most of you know the dash needs to come out. By the way searching with google is a much better way to search the forum than within the forum itself. This has been done several times so I'll just hit the highlights.
First off I have pulled several dashes out doing AC work and this is not really pulling the dash. It's more like pulling the dash cover. I took a couple of photos so if anyone is curious they can see whats underneath. I had already ordered the blower resister due to the fact that the fan would run for a few seconds and stop. The fan itself is a simple DC motor not much to go wrong except for bearings. Most of the work is pretty straight forward, remove the trim to get at the nuts and bolts. A few pointers would be make sure the steering wheel is down and stays down. The upper skirt for the steering wheel is attached the dash frame on one side and the dash cover on the other. It had one plastic screw that I spent more time on than most of the rest of the dash. Don't turn the car on unless the air bag is plugged in! I already knew this but forgot when I got busy testing so now the airbag light is on. the dash has to come out on the passenger side to clear one spot on the right side of the center console. If it were not for that one spot you could lift the dash and pull it straight back and out. All of the foam pads ball up and get in the way but you really can't hurt them. I glued them back into place. It was kind of a fun jigsaw puzzle.Attachment 633967Attachment 633968
Now for the blower motor. Once I got the cover off the blower motor I plugged it back in. I turned the car on with the settings at full and it would spin slowly and then stop. I checked for voltage at the resistor and had 12.8VDC. Then I checked the leads to the motor and had 12.4VDC. Crap the resistor is good but the blower is bad. I quickly whet to the computer and found blower motors from $60 to $400. It's really just a bunch of copper windings and steel laminations so I ordered the cheap one. Back out at the car I pulled the blower and tested it again directly to the battery. Same result, run slowly for a few seconds and stop. A DC motor is such a simple thing, bearings, windings and brushes. As I started poking around with nothing to lose I pulled one of the brush caps and found the spring heated and unspringy and the brush stuck in the brush box.Attachment 633971 I pulled the brush out and cut the wire. I went to the local handyman store and found a replacement of the correct width but it was too long and deep.Attachment 633969 So I took to it with a grinder and made it the correct size and profiled it to fit the commutator. After soldering the wires together and cutting the spring down to the correct size it was ready to test. Attachment 633970When I hooked it up to the battery it almost jumped out of my hand and ground my fingers off. So with the blower fixed I canceled my order for the blower and resistor.
I can't believe how much more air I get now than before. If you turn your blower on high and it does not blow your hairpiece off its probably on the way out. I remember reading about one guy who would just bang on the dash to get his blower running. He's just knocking the brushes loose and some carbon out of the brush box. And too add insult to injury after I got the dash back in I could not get the gauge cluster in. I must have tilted the wheel up when I was working on the dash. So I went to tilt the wheel down and it wouldn't move. I tried to move the seat and it wouldn't move either. Back to the forum to search for a fix. I guess when I was working on the dash I leaned on the seat and unplugged the seat controller. I pulled the broken seat trim and plugged the seat back in. That fixed the steering wheel and seat. Finally I was done. I'm going to run the blower on high for a while to seat the replacement brush.
On one last note, it was interesting to look at how the glove box operates with the dash cover off. You can and I did make some adjustments so it operates smoother and helps to prevent breaking the handle.
01' 750il Chromeline
95 M3 LS swapped
07 M5 Manual
06' M5, Spartan wheels and a 507hp V10
00' 740il Dinan, CAI, Romulus exhaust, Stage 5 engine and transmission tune, 750 brakes, camber plates, strut tower brace. Sold
00' 323i wagon for daughter
03' 525i wagon for the wife, sold
98' 740i for the daughter, wrecked
92' 525i with over 200k, wrecked
02' R1200 CLC, hit by a bus and broken in half. That one made the news!
It's like herpes there is no cure but if treated properly you can live with it for the rest of your life
Wow extremely impressive and great work! Always amazed at threads like this... Its great when a plan comes together especially since AC in this hot simmer is priceless and you fixed it for under $6.
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That's brilliant! This is a DIY that is right up my alley. By any chance, did you take note of the measurements of what the brushes need to be? I can order a brush with spring and wire of basically any size online, but it'd be real handy to know exactly what I need to get. My blower will periodically just go all grumbly and speed up and down of it's own accord or just plain stop working - and yep, a quick smack on the dash sometimes gets some life out of it. Sounds like the brushes to me.
Awesome guide, things like this are what make the forums a real delight. Ways to keep these vehicles going that don't require buying parts that are fast on their way to becoming scarce in OEM form, or abundant in poor quality after market form. Nice work!
Good stuff. I was one of those guys who hit the dash. Mine would not work when the car sat out in direct sunlight.
I added your post to my General info thread on the subject.
https://www.bimmerforums.com/forum/s...eral-HVAC-info
Great write up. Wish I knew about this last month when my blower motor died on the hottest day of the year (102°F heat index) which made my drive home from work miserable. I will definitely try this out with my non-functioning OEM blower motor.
Copy all the above, excellent work. Mysterious boxes of captured smoke are one thing, but DC motors that have been around for ages
are another. Well Done!
This fix is similar to the one for failed window motors - or any motor really. In the case of window motors, the contact area of the copper wires gets fouled as the brushes wear down. With fan motors, maybe it's the brushes themselves that are problematic, probably because fans operate with every drive.
The brush was 3/8" X 5/8" and I opted for one that looked more like graphite than carbon, shiny silver VS. black. What I ended up with was about 3/8" X 3/8" X 1/2" long with a curve that matched the brush that came out. I should have taken one more photo! When I get close to the end on a fix like this I just forget.
01' 750il Chromeline
95 M3 LS swapped
07 M5 Manual
06' M5, Spartan wheels and a 507hp V10
00' 740il Dinan, CAI, Romulus exhaust, Stage 5 engine and transmission tune, 750 brakes, camber plates, strut tower brace. Sold
00' 323i wagon for daughter
03' 525i wagon for the wife, sold
98' 740i for the daughter, wrecked
92' 525i with over 200k, wrecked
02' R1200 CLC, hit by a bus and broken in half. That one made the news!
It's like herpes there is no cure but if treated properly you can live with it for the rest of your life
Nice work! That is great to see that the brushes are serviceable like that. That is usually the most common failure of motors like this. Just a wear item.
So I've read that typically, brushes installed from manufacturing are harder than replacement brushes in order to break in the surface of the motor it contacts. After they wear out, replacements are softer, so as not to continue wearing the motor surface. This would be something to consider when replacing the brushes.
Those dimensions are just the length and width, correct? What is the height we should be looking for?
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If you look at the picture you can see the size of the new brush as it compares to the brush box. The new brush is the width but to long so I ground off both sides until it was square and moved freely in the brush box. After that I ground down the height to about 1/2" and profiled it to the commutator.
As to why it failed I would say that due to sitting the contact surface was bad. Then the brush heated up and conducted that heat to the spring which tempered it and with the loss of spring pressure the problem just got worse. A way to potentially avoid this problem would be to use the car frequently or run the blower on high to clean the commutator. Running at a slower speed via the controller would reduce heat dissipation through the commutator and windings as well as airflow. I used to work on a ship run by DC motors so I have dealt with this problem on a very large scale but it's still all the same stuff.
01' 750il Chromeline
95 M3 LS swapped
07 M5 Manual
06' M5, Spartan wheels and a 507hp V10
00' 740il Dinan, CAI, Romulus exhaust, Stage 5 engine and transmission tune, 750 brakes, camber plates, strut tower brace. Sold
00' 323i wagon for daughter
03' 525i wagon for the wife, sold
98' 740i for the daughter, wrecked
92' 525i with over 200k, wrecked
02' R1200 CLC, hit by a bus and broken in half. That one made the news!
It's like herpes there is no cure but if treated properly you can live with it for the rest of your life
Great post! Model year would help. I’m assuming this fix is applicable to any 740 blower motor, even the later pulsed width speed controlled. Thanks.
- - - Updated - - -
Great post! Model year would help. I’m assuming this fix is applicable to any 740 blower motor, even the later pulsed width speed controlled. Thanks.
It would apply to any DC motor. You just have to find the correct brush, make sure you have a good connection and spring tension.
01' 750il Chromeline
95 M3 LS swapped
07 M5 Manual
06' M5, Spartan wheels and a 507hp V10
00' 740il Dinan, CAI, Romulus exhaust, Stage 5 engine and transmission tune, 750 brakes, camber plates, strut tower brace. Sold
00' 323i wagon for daughter
03' 525i wagon for the wife, sold
98' 740i for the daughter, wrecked
92' 525i with over 200k, wrecked
02' R1200 CLC, hit by a bus and broken in half. That one made the news!
It's like herpes there is no cure but if treated properly you can live with it for the rest of your life
Can you re upload these pics? They're not working anymore. Im in the middle of this now and am about to order a new blower motor assembly but would like to try this first. Does it eliminate the squeeky noise as well?
I'll see if I can dig them up. My blower did not make any noise, your bearings may be worn and need some lube.
01' 750il Chromeline
95 M3 LS swapped
07 M5 Manual
06' M5, Spartan wheels and a 507hp V10
00' 740il Dinan, CAI, Romulus exhaust, Stage 5 engine and transmission tune, 750 brakes, camber plates, strut tower brace. Sold
00' 323i wagon for daughter
03' 525i wagon for the wife, sold
98' 740i for the daughter, wrecked
92' 525i with over 200k, wrecked
02' R1200 CLC, hit by a bus and broken in half. That one made the news!
It's like herpes there is no cure but if treated properly you can live with it for the rest of your life
Thanks. I was able to pull up the contacts and found that one side had the plastic housing cracked pretty good and a bunch of debris. This was probably my issue all along. Leaning toward replacing it at this point but would still like to see this for future reference. Anybody know how long these motors/resistors last? I think my dash was pulled at some point so it looks like the resistor was replaced once but not the blower motor.
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