Auto question - getting my electric mirrors working

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Che_Guitarra

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Dec 22, 2012
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I know this is off topic, but it involves a general electronics topic which is falling silent on other forums i've tried.


I recently bought a car and the previous owner had installed aftermarket side mirrors.  They've never worked.  I pulled the door skin off today and immediately saw the problem - no connection.  Then I saw the factory electric mirror loom has a four pin output, but the mirror only has three pins.  And the connection headers are incompatible.

IMG_0313_zps69bef497.jpg



Further poking around and this is factory schematic for the electric mirror:

Mirror_zpsf40ad388.jpg



So i'm trying for a fix.  Firstly, does anyone know that the symbols between wire #2 and #3 represent?  I'm guessing one on the left could be a switch, but the rectangular symbol is a complete unknown.  Google isn't helping me.  Can anyone fill me in?

I'm guessing of the three wires in the mirror, one is for X axis, one for Y, and one must be for ground.  I'm not entirely sure what's going in the factory loom but there must be some kind of axis flipping going on to get two directions of travel per axis.  Schematic also indicates a heating element which I don't intend to use (we don't get freezing temperatures in my area).


Can anyone take an intelligent stab in the dark at a solution?  Or is a solution impossible?


Can clarify with more info in the morning after a good sleep  :)
 
Mirror heater is my bet.

Many mirrors are heated, and most have a thermostatic cutout to prevent OVERheating.

If you view the 'square zigzag' as a resistive heater element, powered by a thermostatic relay, which opens and closes with respect to temperature (on cold days it's going to want to STAY on until it reaches temperature, then cycle with a mark-to-space ratio dependent on how cold it is outside (colder days lost heat faster than warmer ones). On warm days it's going to want to turn off FAST or warp some plastic.

Mind you, I don't see two motor axes on that diagram. I would expect a vertical and horizontal motor, but it depends on the vehicle. -What's the car, and are the mirrors OEM or aftermarket... or from a different model or market? (there's a fashion for fitting RHD mirrors to LHD cars and vice-versa, as well as 'Emfree' ["M3"] mirrors to other cars)
 
+1  it looks like a heat element.

Pin 1 and 2 are motor drive, probably flipped to change direction. Pin 3 is probably fused power to the heater. Pin 4 may be the spare parts, or an unused auxiliary power feed to perhaps some other active device.

JR

[edit- unless the second mirror has two motors and two axis of rotation without heater...

Can you find any info on that mirror? /edit]
 
I've replaced mirrors on both my Audi (Upgraded to heated, dual-axis motorized dual-view [Non-DOT-approved, although permitted in every other country I've ever driven in, and VASTYL more useful than the DOT-standard flat-plane-driver's-side-and-shrink-view-passenger-side]) and on the Porsche to dual-axis, motorized dual-view... The Porsche was tricky, the Audi was easy. -I know that it varies significantly from manufacturer to manufacturer.

Just returned my rental car one week ago yesterday, after driving through Europe, including trip to both the Mercedes and Porsche factories in the Stuttgart area. -The rental car (A VW Golf wagon) had heated, dual-axis motorized, dual-view mirrors on both sides, and was exactly what I was used to... I wish the American DOT would get over its torpor regarding headlight patterns (though I do appreciate the concerns about unlit overhead signs) and mirrors. -Oh, and the adaptive headlamps are fantastic. -Also the "ramped" turning lights (like the old Mercury/Lincoln 'switched' lights, but MUCH less sudden, and progressive with steering angle) were a nice discovery, also.

Anyhow, I'm digressing. -Can you give us more info on the car and mirror? -Possibly a bit more from around the zoomed-in part of that schematic?

Cheers,
Keef
 
Wow, thanks for the responses guys.  The car is this 1997 BMW 328i: 

IMG_9744_zps1fff895f.jpg



The former owner installed some M3 style mirrors - I can't find any info on the brand (KDM) but the construction quality of the shell and motor drive system is flawless... I don't understand why they wouldn't be made to be plug-and-play.  But they are what they are, and certainly cheaper to try figure them out than buying OEM mirrors.

Here is the circuit I can go off... not sure how to regress further back into the loom... the schematics aren't laid out in an intuitive fashion.


Mirror1_zpsc565aadb.jpg
 
In that diagram

A - switched earth to activate the motor (passenger side)
B - switched earth to activate the motor (driver's side)
C - permanent live feed
D - switched live feed to activate the heated mirrors

I assume the relay has a bimetallic strip that drops it out above a certain temperature. The dotted line linking 1, 2 & 3 signifies a connector

There is no method with this setup to allow two axes of movement. There's also no method of reversing the direction of the mirror movement unless A and C reverse polarity to reverse motor direction. If that's the case then A or C would have to be a permanent live otherwise the heater won't work

The devious way of doing this would be to feed the motor with a live feed to both A and C and have the switch earth A to move the motor in one direction and earth C to reverse it.  There's a problem with this idea as C is common to both sides… When C is earthed the heated element will stop momentarily

Car electrics are wonderfully devious. Switched earths are a really clever way of doing things like interior lights. Mercedes W124s have a diode feeding the electric window circuit so the front windows operate when the doors are open and the ignition off.  When the doors are shut the windows won't open unless the ignition is on

Nick Froome
 
If it only got one motor, how can it do X and Y?

(I can think of ways but more complicated than just another motor.)

Here's how an older cheaper car did it. Two motors per mirror (no heat). Driver gets one control panel with a left-side / disable / right-side switch, and a GameBoy-like 4-way joypad.
 

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I'm baffled about the single motor and no obvious way to switch polarity of the wires feeding the motor... I too don't see how it changes direction.

Is there (or rather, WAS there) a mechanical adjustment for one of the axes?

The M3 (or as I mentioned "Emfree" in Cockney) explains to me why the mirror was swapped. There are plenty of aftermarket "M3" type mirrors, and it's a source of fascination and amusement that people are willing to fit them for an absolutely negligible aerodynamic advantage. -I suppose that the 'real' advantage is the 'suggestion' that this is a performance variant, but the only people who will see that are deeply brand-familiar, and will probably spot other clues which identify it as 'mirror-swapped'...

I say that not to judge or ridicule, but as an observation. -Certainly, the owner BEFORE you probably must have the calculation and decided that the inconvenience of non-working mirror motors was outweighed by the admiring glances that the upgrade brought.

So the next question is: are all genuine M3 mirrors 4-pin, and if so do you have access to a wiring diagram for those? -Also, do you have access to a multimeter, and can you tell me what happens across the two motor pins of the 3-pin connector when you move the control one way or the other?

Also, what does the controller look like? Is it a 2-axis joystick, or a single-axis 'rocker' which moves the mirrors inwards/outwards (or upwards/downwards) only?

Nice car, by the way. I likes me some unmolested BMW's, although far too many of them around here are destroyed (in my eyes) by people piling on the "improvements".

Last week I was in Germany, and since we were in Stuttgart I took the family around the Mercedes and Porsche factories (we have a Porsche and a couple of Mercedes along with my daily Audi... addicted to German cars now!) -To see how large stampings and how automated production lines have become is thought-provoking. -The amount of adhesive-versus-weld in modern cars is also a little surprising.

Anyhow, I digress. -Can you show us a photo of your controls, and find out if genuine M3 mirrors have 4-pin plugs? then mybe we can work out what's going on.

Cheers!
Keef
 
Genuine M3 mirrors are supposed to be plug and play across all E36's, so I can only assume they're four pin.  Actually I know they're four pin based on various confirms i've received over the last couple of days.

Mirror control is basically a N/E/W/S joystick with a switch to flip between left and right.


I know what you mean about silly mods.  The previous owner seemed to have an M3 infatuation... I don't.  I bought the car because of its condition, low kms, and the 15 year dealer service history.  I've spent the last three months ironing out the fad inspired unimprovements, now it's just a solid 328i... but i'll keep the M3 rims thanks, lol  ;) ;D
 
Well, with a two-axis joystick, it's hard to see how the posted schematic can be accurate...

With three pins, I'm guessing that the mirrors are UNheated. -Assuming that there are two motors there and one shared ('common') connection, the test that suggests itself to me would be to measure resistance between pairs of pins. -You should see twice the resistance between two pins than you do between the other two pairs, suggesting that the UN-measured pin (under that test) is the common.

If you can then hook a multimeter (reading volts) onto the connections coming from the car and try to identify which pair of pins swaps polarity as you switch east/west/east/west, and then which pins swap polarity as you swap north/south/north/south, then you SHOULD be able to identify one contact common to both.

Then it's a question of either splicing or sourcing a mating connector to make things fit... Often I like to make adaptor harnesses with (in this case) both 4 and 3-pin connectors, but I know that things get pinched around door jambs, so that may or may not be possible here.

Let us know your multimeter findings, if you can.
 
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