A few tips on installing e28 window motors

jmackro

jmackro

Well-Known Member
Messages
2,520
Reaction score
811
Location
San Juan Capistrano, Ca.
OK, so why does e9coupe.com need yet another thread about installing e28 window motors? Well, I thought I could pass on a few tips that I learned while converting both front doors on my 1970 2800CS from the original "sardine can" style motor & gearbox to the e28 style with integrated motor/ gearbox. These are things that I figured out on my own, and didn't find documented elsewhere.

The best reference that I found for this conversion are the two websites created by e9coupe.com contributor kurtd at:

https://sites.google.com/site/kdelimon/windowmotorconversion1

https://sites.google.com/site/kdelimon/windowmotorconversion2

Those sites are terrific, but I have a few things to add and/or things that I did differently. Where I differ from the kurtd recommendations, I'm not suggesting that my way is better; I'm just offering an alternate approach that made more sense to me.


1) CHOICE OF MOTOR

The right door of the e9 (passenger side door) uses the e28 motor with the part number 12V 1730 821 027. I believe that motor comes from the left rear of the e28. The left door of the e9 (driver side door) uses the e28 motor with the part number ending in 026. Note that the drive gear on the gearbox will have 8 teeth - later motor/gearboxes with 10 teeth won't mesh properly with the large gear on the window regulator.

The first photo (thanks to hbchris) below shows a pair of e28 motors, and demonstrates the motor/gearboxes' "handedness". The second photo shows how a p/n 027 e28 motor fits a right front e9 regulator.

BMW motor pair cropped.jpg
BMW reg motor parity.jpg
 
Last edited:
2) MODIFICATIONS TO MOTOR

I disconnect the e28 motor from its transmission by removing the two torx head screws and rotate the motor 180 degrees (the motor won't separate from the transmission - it just becomes loose enough to turn). By doing this, the bulge on the side of the motor where the two wires exit does not interfere with the regulator sheet metal.

kurtd's website doesn't discuss this modification; instead it recommends a cut-out in the regulator sheetmetal to clear the wire bulge. Note that the regulator sheetmetal still needs to be relieved to accommodate the motor - this mod just reduces the amount of metal that needs to come off.

A second benefit of this modification (at least for me) is that it positions the motor wires in the vicinity of the original e9 connector, so there is a shorter run and neater routing of those wires. The second photo below shows the relative positions of the wires exiting the modified motor and that connector.

The first photo below shows the unmodified e28 motor just sitting on an un-trimmed regulator. The second photo shows the gearbox with the motor rotated. The third photo shows a right front e9 regulator cut to accommodate the e28 motor (and yes, my cutting was a bit sloppy).

BMW motor before.jpg
BMW motor after.jpg
BMW regulator notch 2.jpg
 
Last edited:
3) MODIFICATIONS TO DOOR SHEETMETAL

The e28 gearbox is thicker than the e9 gearbox, which results in interference with the inner door sheetmetal. Part 2 of kurtd's website explains how to install spacers between the regulator and inner door metal to relieve that interference. Instead of doing that, I just cut a bit of metal away from the inner door sheetmetal. To me, this was the better approach as it allows the regulator to be positioned as the factory had intended.

Make a paper tracing of the shape of the gearbox back. Temporarily mount the regulator to the door (you can't fully tighten the bolts before trimming the sheetmetal, but it will be positioned properly fore-aft, up-down). Orient your tracing to the part of the gearbox that shows, and mark the outline of the hidden part of the gearbox. It should look like the shape in the picture below.

The first photo below shows the metal that needs to be removed. The second photo shows the regulator with an e28 motor and gearbox installed on a trimmed e9 passenger door.

BMW door cut out lines.jpg
BMW window motor door cut out 2 (2).jpg
 
Last edited:
4) ADDING RELAYS

Kurtd's website shows how to re-wire the console switches to power 2-wire e28 motors. But the 40+ year old switches and wiring in your e9 will add resistance to the connection between your window motors and battery, reducing the current reaching the motor. Instead of using that wiring for power, I run a heavy-gauge wire to the door to supply +12V to relays that power the motor. The console switches now only need to supply a few milliamps to trigger the relays.

Different relays and wiring is needed for the 2-wire e28 motors than is used for 3-wire "sardine can" motors. Two SPDT relays per motor are needed - I found these on ebay. One relay is energized for "UP" operation, the other for "DOWN". Someone published this schematic e9coupe.com some time ago (sorry to not recall who posted it and give them credit). The two wires going to the relay coils that are labeled "+" and "-" connect to the output from the console switch and to ground respectively.

Window motor e24 schematic.jpg
 
Last edited:
teahead said:
"The right door of the e9 (driver side..."Typo? Or you have a RHD e9?
Click to expand...

Typo, yes. Thanks for the pick-up. Edit made.

Simufly said:
Does this upgrade work if you have the later non sardine can motors?
Click to expand...

Sorry, I just don't know. All my experience is with my 1970 2800 CS. Lots written here on e9coupe.com about this conversion; perhaps another thread gets into the relative performance of e28 versus the later non-sardine can motors
 
I'll repeat what I've stated in a couple of other threads. My '74 with the newer OE window motors was about 20 seconds up or down for all four windows when I bought the car. Changed to e28 motors in all four windows, completely removed/cleaned rear window systems, and cleaned tracks etc. on front window systems. With the e28 motors, all four windows are now about 6 seconds up or down.

Gary
 
Gary Knox said:
I'll repeat what I've stated in a couple of other threads. My '74 with the newer OE window motors was about 20 seconds up or down for all four windows when I bought the car. Changed to e28 motors in all four windows, completely removed/cleaned rear window systems, and cleaned tracks etc. on front window systems. With the e28 motors, all four windows are now about 6 seconds up or down.

Gary
Click to expand...

My '73 has issues with the rear windows most. The passenger side screams like a banshee when lowering. I've found posts about replacing the front motors with E28 motors - but yours is the first I have seen referencing a rear motor conversion. Did you use the same E28 motors?
 
TG-2002-320i-328ci said:
My '73 has issues with the rear windows most. The passenger side screams like a banshee when lowering. I've found posts about replacing the front motors with E28 motors - but yours is the first I have seen referencing a rear motor conversion. Did you use the same E28 motors?
Click to expand...
Start with good cleaning of whole mechanisms, old grease on rails is more like glue & pretty often motors are secondary problem.
 
TG-2002-320i-328ci said:
My '73 has issues with the rear windows most. ... I've found posts about replacing the front motors with E28 motors - but yours is the first I have seen referencing a rear motor conversion. Did you use the same E28 motors?
Click to expand...

Sorry, I just saw your post (5 months late!). Note that my posts are about e9 FRONT doors. You use e28 REAR motors for e9's (I have no idea what e28 front motors look like).

In post #13, Mulberryworks reports that the e28 rear motors can also be adapted to e9 rear regulators, but I have not done that conversion myself. I still have the "sardine cans" at the rear.
 
Last edited:
Thanks for the post. I suspect it will be needed if I'm sucessful in my aquistion.

20180523_201318.jpg
 
wtinker said:
Thanks for the post. I suspect it will be needed if I'm sucessful in my aquistion.
Click to expand...

Judging from that photo, speeding up the power windows will be about the 315th job on your list! Are you going to pick up a 5-speed manual transmission while you are at the wrecking yard hunting for e28 rear window motors?
 
74 front pass reg a.jpg
74 front pass reg a.jpg
Figured that I would throw in my cars application since I just ordered and received some E28 motors and am working on installing them. So my car is a 74 3.0 CS. I have put a few pics here to help. My old motors were the black ones in the pics. I had to remove them while still in the door to get the window mechanism out of the door. No big deal. I had looked at all the great info Jay put out there and was prepared to do some cutting. So far I think that I got a break with the 74 since the E28 motors will bolt right into the mechanism. Not sure if the mechanism and motors were original or had been swapped out over this cars life.

Where I may have a problem and was looking for a little insight is on the mechanism. At first I put it in a vise to see if I can move it. Not a chance so I have it soaking in PBB. Should I be able to move it by hand? Also without the mechanism on the door it is still somewhat hard to move the window. Any tips on grease to use for lube?
 
Beginning in Feb or Mar of 73 the motors changed to the ones you have so they bolt right in. In my mind the torque is the same as e28 as I have swapped mine and speed is similar, cleaning and greasing the tracks makes the greatest difference.
 
I found the best thing to do was pull the mechs completely from the car so you could clean all the grease and crap thats accumulated over 45 years.

A whole load of wurth motor cleaner / brake cleaner, some fine wire wool in the mechanisms to make sure its all smooth and then I used a high quality teflon grease
 
You must log in or register to reply here.
Back
Top