Reversed electric window.

[ss2115]

This ones got me a bit tricked.
I finally found time today to take my rear door apart to determine why the electric window had stopped working.

I found the metal part of the motor housing had a screw loose and had backed away from the plastic gear section on an angle and jamming the motor from turning.

I took it off completely to inspect it for any damage.
I cleaned the commutator, slipped the brush section back over it and reassembled the motor back together on the gear section with a new screw and some screw thread to make sure it wouldn't pull out again.

Everything works okay again except the window goes down with the up button and up with the down button - both on the door switch and the centre console.

I know it would be easy to swap the two wires over at the plug, but what gets me is how this could possibly have happened!!!
1) The metal body can go back on either way 180 degrees apart.
2) The plastic section that holds the brushes can only go in one way because it has a rectangluar rubber grommet that fits into a cut-out on the plastic gear section - ie: it guarrantees that the brush body is right side up as well as orientated to the correct exit from the motor.
3) the two wires from the motor plug into the loom with an orientated plug - its not possible to swap polarity.

Any ideas?

[whiskychaser]

When you have eliminated the impossible, whatever remains, however improbable, must be the truth - Sherlock Holmes

My guess is magnets in the cover are 180 degrees out from their design position.

[tim eh?]

ok I'll play - how about the switch on the door being backwards?

[ss2115]

When you have eliminated the impossible, whatever remains, however improbable, must be the truth - Sherlock Holmes

My guess is magnets in the cover are 180 degrees out from their design position.

On one hand I have to agree with you as its the only possible variable, but on the other hand its a permanent magnet motor - the poles of the magnet face the same way to the comutator and stator windings no matter even if they are rotated 180 degrees.

I'll be trying this today anyway.

[ss2115]

ok I'll play - how about the switch on the door being backwards?

It can't be - the switch can only plug on one way with a triangle and round peg to guarrantee orientation.
The coloured white arrow is pointing up and the unfilled arrow pointing down - just like all the other doors.

No - its not a puzzle. Its a genuine problem that I cannot understand.

[Ross]

I don't see the magnet thing being the issue if the swap would have been 180* out. Damned if I know though. Are you sure the brushes aren't somehow crossed?
I've played with DC motors a little and know changing the position of the magnets can effect speed, perhaps enough to reverse the motor???

[whiskychaser]

on the other hand its a permanent magnet motor - the poles of the magnet face the same way to the comutator and stator windings no matter even if they are rotated 180 degrees.

I'll be trying this today anyway.

If I said the windings were different lengths or the brush offsets were different you would say I'm having a laugh. Particularly if I mentioned Fleming's Left Hand Rule Thats why I just said its not together as it was designed. Hopefully the window was fully up/down when you took the motor out

[ss2115]

I don't see the magnet thing being the issue if the swap would have been 180* out. Damned if I know though. Are you sure the brushes aren't somehow crossed?
I've played with DC motors a little and know changing the position of the magnets can effect speed, perhaps enough to reverse the motor???

The brushes are a permanent part of a plastic plug that slides down into the metal casing and you pull the brushes back to let them pass over the end of the comutator.
The plastic plug then settles against the end of the magnets inside the metal casing.

On the upper side of the plastic plug, the two brushes come to two little tangs set in the plastic on to which are soldered the two cables that go to the door wiring loom.
These soldered wires are only about 3mm long and then go through a rectangular rubber grommet which is molded/glued to the cables so it cannot be moved along the wires and forms a waterproof seal.
Thus - once the brushes have been placed down into the metal body, the orientation becomes fixed because the rubber grommet slides into a cut-out for it when the metal section is screwed back up to the plastic gearbody.

The absolutely only thing that can possibly be changed (that I can fathom) is that at the beginning, the plastic plug with the brushes can be placed into the metal body one of two ways 180 degrees apart. Once they are inserted, everything else has to go one way only from that point on.

Its the one and only variable, but my knowledge of permanent magnet motors (E&C Certificate) tells me it shouldn't matter as the magnets have north and south poles and it wont (shouldn't) matter which way the housing is rotated around the stator.

I'm flummoxed!

[ss2115]

If I said the windings were different lengths or the brush offsets were different you would say I'm having a laugh. Particularly if I mentioned Fleming's Left Hand Rule Thats why I just said its not together as it was designed. Hopefully the window was fully up/down when you took the motor out

Yes - it had jammed in the fully up (closed) position and has been that way for a few weeks.
When I withdrew the motor housing from the plastic gear section, the worm gear just nicely slid out and the window never moved.
Getting it back in was a little bit more difficult, but I just sat there and wiggled the motor housing section up and down without pushing too hard and the worm gear/stator turned little by little until the motor housing finished back up flush with the gearbody and I was able to insert the screws.

[Ross]

"The absolutely only thing that can possibly be changed (that I can fathom) is that at the beginning, the plastic plug with the brushes can be placed into the metal body one of two ways 180 degrees apart. Once they are inserted, everything else has to go one way only from that point on."
This has to be it