Upgrading and replacing 911SC (1978-83) flag mirror motors (for less than $100)
 

Porsche’s flag mirrors are in some ways a perfect example of ‘engineering gone wild’. I imagine the Zuffenhausen engineers sitting around one day, daring each other on who could make the most complicated adjustment mechanism with the strangest assortment of parts. The ‘single motor, plastic clutch, reversing current, and… dental floss!’ design won, apparently.

After repeatedly repairing, replacing, and repairing again these early plastic behemoths, I figured it was high time I found a more permanent, and modern, solution. I had read about others replacing the originals with a VW/Audi mechanism, and while there are some great write-ups that talk about the electrical modifications, in this article I’ll try and give a full step-by-step guide along with some of my learnings along the way.

…And all for significantly less than $100, which in my experience doesn’t even buy you a single ‘used’ old style motor.

A couple of caveats:
- The below procedure is pretty much non-reversible due to cutting off some of the original mirror plugs/wiring harness etc.
- Although I’ve tried my best to be accurate with all of my pictures and descriptions, your mileage may vary and proceed at your own risk!
- Your existing wiring needs to be complete and operational (even if the motors are broken). I had a broken wire which I had to track down and replace as part of this… here’s hoping you don’t need to do the same – painful!
- I couldn’t find the mirror motor I used on Pelican, so I’ve shown a pic of another site…
- When you’re finished, Left/Right controls will work normally, but pushing ‘Up’ will actually move the mirror ‘Down’, and vice versa. While I could have fixed this by making further modifications to the new motors, I chose not to – I got used to it in about 8 seconds and haven’t thought about it again. If you’re a purist, well… this probably isn’t for you anyway.
- I did this over a couple of weeks, with lots of ‘thinking time’ thrown in. I’d estimate about 2 full days for someone to do this from scratch.

What we’re going to do is replace this:

http://forums.pelicanparts.com/uploa...1526266817.jpg

with these:

http://forums.pelicanparts.com/uploa...1526266817.jpg

http://forums.pelicanparts.com/uploa...1526266817.jpg


http://forums.pelicanparts.com/uploa...1526266943.jpg


Materials and tools required (pics below):
- 2x mirror motors from a VW mk4 golf (link) ‘VW Jetta Golf GTI MK4 Passat Audi A4 – Genuine’
- 2x 12v DC 10A DPDT (Double Throw Double Pole) relays (link)(link)
- 6x M3x35mm bolts (3 per side)
- 8x M3x15mm bolts (4 per side)
- 14 M3 nuts (7 per side) to fit above bolts
- Washers to fit the above
- 22x female 2.8mm blade connectors (11 per side)
- 16x 6” lengths of wire (8 per side). Similar gauge to what your existing mirrors use – 16-14ga is fine. A variety of colours would be useful, but not critical.
- 12x 4mm male and female bullet terminals (6 pairs per side)
- Rubber tape or some other type of waterproofing material (I re-used the rubber surrounding from the old mirror motor)
- Touch up paint (any colour)
- Blue Thread-loc
- Wire wrap/dressing (if desired)
- Zip ties
- Test lamp
- 8mm and 3mm sockets
- Screwdrivers
- Crimping tool
- Drill and drill bits of various sizes
- Tin snips
- Old towel or large rag
- Notepad
- Some flat tin to fabricate the bracket (I used an old cookie tin)

*** NOTE: I did this mod about two years ago (yes, it’s taken me that long to write this up and post…). After driving with this for awhile, I noticed I was getting a LOT of vibration in the mirrors due to the tin being too thin. I’ve now designed and 3D printed new brackets, which no longer vibrate. See the very end of this post for more info…. Or, just use thicker tin/metal for the brackets.

http://forums.pelicanparts.com/uploa...1526266943.jpg

http://forums.pelicanparts.com/uploa...1526266943.jpg

http://forums.pelicanparts.com/uploa...1526266943.jpg

http://forums.pelicanparts.com/uploa...1526266943.jpg

(This is the tin that ended up being too flimsy. I'd strongly recommend replacing with the 3D printed version at the end of this post...)

Next post, we start dismantling...

Remove the old mirror
1. Drape a towel between the flag mirror and the car to protect your paint.
2. Carefully pry the mirror off of the backing plate by slipping a flat head screwdriver between the plate and the mirror and gently twisting and prying. Disconnect the heating wires and et the mirror aside
3. Remove the 3x 8mm bolts securing the rubber housing to the flag mirror
4. Separate the rubber housing away from the flag and unplug the wiring harness. Take the rubber housing to the workbench.
Confirm the existing wiring is operational and confirm wire colours
5. Examine the colour of wires coming out of the plug coming out of the hole at the base of the flag mirror (i.e. still attached to the car). Note that there are six holes/wires at the plug, but two of them are for the heating element and can be ignored for now. Draw a table similar to the one below, with the four wire colours down the left side, and the four directions (Up/Down/Left/Right) across the top.

http://forums.pelicanparts.com/uploa...1526267375.jpg

http://forums.pelicanparts.com/uploa...1526267375.jpg


6. Connect the ground lead of your test lamp to a suitable ground point.
7. Turn on the ignition of the car to ensure you have power to the mirror. Ensure the mirror selector is switched to the mirror you’re currently working on.
8. Insert the point of the test lamp into the first of the plug holes, ensuring you’re making good contact with the wire connector inside the hole.
9. Move the mirror joystick up, down, left, and right, and take note which of the directions the test lamp illuminates.
10. Repeat for each of the holes until you have completed your table.
11. The hole that lights for both Up and Down powers the solenoid. Put an ‘S’ on your table next to this colour.
12. I found that the connections inside my plugs was not reliable, so I chose to cut the plugs off and replace with standard male/female bullet connectors. YMMV; however, ensure that your test lamp lights reliably, consistently and strongly for each direction.
13. Set aside this table for now. Remove your test lamp and turn off the ignition.

Disassemble old mirror housing
14. Using a marker, put an ‘Up’ arrow on the mirror backing plate. Then drill out the four rivets from the front of the backing plate and separate the plate from the motor assembly.

http://forums.pelicanparts.com/uploa...1526267451.jpg

15. Using a screwdriver, pull aside the rubber sleeve and remove the three screws holding the mirror assembly from the rubber housing. (Set these three screws aside, as they are required later)

http://forums.pelicanparts.com/uploa...1526267503.jpg

16. Set aside the mirror assembly. If you plan on using the wiring harness and plug, cut the wires as close to the motor as possible.

Next, on to the mounting bracket fabrication

Mounting brackets fabrication

17. Take the mirror backing plate and place on the workbench face down with the ‘Up’ arrow facing away from you. Take the new mirror motor and place it on the back of the backing plate with the ‘Top’ label aligned with the top of the backing plate, and centred as best as possible.
18. Now we are going to mark and drill the location of the four mounting holes on the backing plate. This is the trickiest part of the process, because the holes end up being right on the edge of the contours of the plate. The more carefully you mark and drill these holes, the closer your mirror will be to being centred in the rubber housing in the end. In the picture you can see that the bottom two holes weren’t very centred – luckily I had a spare plate so just re-did it. You pretty much want to be drilling right where the curve of the raised square is - like the top two holes in this picture.

http://forums.pelicanparts.com/uploa...1526267687.jpg


19. Test fit the motor using the M3x 15mm bolts. You want as little of the motor hanging over either side of the plate as possible.


http://forums.pelicanparts.com/uploa...1526267745.jpg

http://forums.pelicanparts.com/uploa...1526267745.jpg

(Ignore the wires in this picture. Just concentrate on centring the motor)

20. Take an M3x35mm bolt and apply some touch up paint to the end. Drop the bolt through the three mounting holes that go through the mirror motor, to mark holes on the backing plate.

*** NOTE - if you're going to use the 3D printed backing plate, you can ignore the next few steps. Just download and print the plates and skip to step 27...

http://forums.pelicanparts.com/uploa...1526267897.jpg

21. Remove the motor from the backing plate, and drill three large holes through the backing plate on the marks. The holes should be big enough to allow the head of a screwdriver to fit through – I would suggest making them about twice as large as a screwdriver shaft to give some adjustment space. You can resize these later if required.

http://forums.pelicanparts.com/uploa...1526267943.jpg

22. Re-attach the motor to the backing plate. I used some blue thread-loc to secure.
23. Take the (now empty) rubber mirror housing and the flat tin. Using tin snips, cut the flat tin to the shape of the hole, being careful to a) completely cover the opening and three inner screw holes but b) not cover the three outer bolt holes. In this picture, the tin is partially covering one of the bolt holes – I trimmed this back later. Note that the tin sits on the back of the rubber housing, not inside it.


http://forums.pelicanparts.com/uploa...1526267993.jpg

http://forums.pelicanparts.com/uploa...1526267993.jpg

24. Mark and drill the three screw holes.


http://forums.pelicanparts.com/uploa...1526268059.jpg

25. Using the three machine screws from the original motor assembly, attach the tin plate from the back of the rubber housing. I.e., you’re now putting the screws into the housing from the outside, rather than the inside.

http://forums.pelicanparts.com/uploa...1526268143.jpg

26. Take the backing plate and motor assembly and place inside the rubber housing, so that the motor rests on the tin plate. Gently push the motor in all four directions to ensure it can move freely.
27. You may find that you need to trim away the two small rubber tabs on the inside of the housing, in order for the motor to move up and down freely. Use the tin snips to do so (carefully)

http://forums.pelicanparts.com/uploa...1526268179.jpg

28. Once you’re satisfied with the placement, use the touch-up paint and long M3 bolt to mark the position of the mounting holes on the tin plate. Drill the three holes in the tin plate (visible in the picture above – note that my original positioning was poor, so there’s an extra hole). Test fit the bolts, then remove the plate and motor assembly.

29. Take note of which side of the motor the wires feed into. Cut a small tab out of the tin plate to allow the wires to exit to the rear of the housing. (The location of this tab is different on the Left and Right mirror). The picture below shows the tin plate with the three machine screws securing it to the rubber housing, the three bolts securing the motor to the plate, and the dressed wires exiting the tab.

http://forums.pelicanparts.com/uploa...1526268336.jpg

Overview of the wiring

In order to connect the wiring together correctly, it will be helpful to understand the original motor’s operation, the new motor’s operation, and the role of the relay in the new design.

Porsche’s original design utilizes a single motor, in conjunction with a solenoid connected to a small arm or ‘clutch’.

http://forums.pelicanparts.com/uploa...1526268409.jpg


There are four wires in this design:
- Two wires to the motor (Blue and Black). The joystick switch is wired such that the polarity of these wires changes to spin the motor clockwise or counterclockwise, depending on if you push left or right, or up or down.
- Two wires to the solenoid (difficult to see in the photo, but White and Brown). The solenoid is actuated by pushing the joystick, and is either ‘Closed’ or ‘Open’. When ‘Closed’, the motor spins one set of the geared spools. When ‘Open’, the arm engages the clutch so that the motor spins the other set of geared spools.

From your earlier testing of your wiring with your test lamp, you should see that when you push Left or Right, the Solenoid is not activated. The Motor will simply spin either CW or CCW, depending on which way you push the joystick. When you push Up or Down, the solenoid AND the motor are engaged. The arm pushes the clutch across (down in this photo), and the Motor spins CW or CCW. These actions cause the twine that you can see in the photo to wind/unwind and thus pull the mirror in one direction or another.

(The arm/clutch assembly has a habit of getting stripped/stuck/not working correctly, resulting in the mirror only being able to move in one plane – usually Left/Right. This is what happened to one of mine; on the other one the Solenoid just died completely.)
The replacement motor uses a completely different setup. It has two motors within the housing, one for Left/Right, and one for Up/Down. It also only uses three wires to accomplish all of this!

http://forums.pelicanparts.com/uploa...1526268487.jpg

So how does it work? Well, you could look at the wiring diagram for a VW or an 84-89 Carrera’s mirrors and try to decipher what the joystick switch is actually doing, but for the purpose of what we’re trying to accomplish, we don’t need to know that. In fact, we don’t WANT to know that – what we need to figure out is how we use the existing wiring to power these two motors.

We can see that there are three wires (pins) in the picture, and the middle pin is shared by both motors. DC motors are pretty straightforward. Apply Power to one pin and Ground to the other pin, it will spin in one direction. Reverse the wires, and it will reverse direction.

We know from looking at the picture of the original motor/solenoid setup, that we already have two wires that can provide reversing polarity – there are two wires that come in to the motor (Blue and Black) – and the motor spins in two directions. Those wire colours don’t correspond to the wiring harness on the car, but we know from our testing with the test lamp, that there are two wires providing L/R and U/D – for me it was the ‘Black + Blue Wires’ and the ‘Black/Green wire’. The Double White wire is the solenoid, with the Double Brown wire.

http://forums.pelicanparts.com/uploa...1526268551.jpg

When you push Down OR Right, the Black + Blue wire is positive, and the Black/Green wire acts as ground.
When you push Up OR Left, the Black + Blue wires act as ground, and the Black/Green wire is positive.

So we’re halfway there – with those two wires, we can control one of the motors. Remember that in the original design, a solenoid physically moved the arm to engage different spools. By adding a ‘Double Pole, Double Throw’ relay, we use a solenoid to physically move the connection, so that the two wires connect to the second motor. The below wiring diagram shows exactly what’s happening:

http://forums.pelicanparts.com/uploa...1526268609.jpg

The square box represents the relay, with the solenoid at the bottom. M1 and M2 are the two motors within the single motor housing.

The Black + Blue, and Blue/Green wires, are ‘normally’ connected to Motor 2. Let’s call this the Left/Right motor.

When the solenoid is engaged by applying power to the ‘Dbl White’ and Brown wires, the two arms inside the relay both move, so that the two wires are now connected to Motor 1. Note that when this happens, Blue/Green is still also connected to Motor 2 – but because the other wire connecting to Motor 2 is now disconnected, the motor doesn’t (cannot) work.

Pretty nifty, I thought. Hopefully you were able to follow along. There is a possible situation that could arise out of the above ‘shared third wire’ that some of you may have already deduced. But I’m getting ahead of myself. Now that we understand how the relay needs to be wired together, we can proceed with assembling the harness and connecting it all together.

Phew, you have done better than me. I just shoved some Blutack in there to keep it in the right position.

Prepare the wiring harness and connect the relay

30. Note that there are eight pins on the relay; If you are NOT planning on reusing your existing plugs and wiring, cut eight wires approximately six inches in length. If you are reusing your existing wiring, you will only need four additional wires. Some notes on wire colour:
a. Four of these wires are going back to the existing wires at the car. Match these colours to the car wiring colours if possible. Otherwise label each wire with its corresponding colour.
b. Four of the wires will go to the new motor; two of the wires will be crimped together at one end so should be the same colour.

31. On one end of EACH of the eight wires, crimp a female blade connector. If you are reusing your existing plug, crimp the female blade connector on to the four wires (ignoring the two for the heated mirror). Either way, you should now have eight wires with female blade connectors. These will all attach to the relay.

32. If not re-using the existing plug, take the four wires that will go to the car side, and crimp a male bullet connector to each. Cut the plug off at the flag mirror, and crimp female connectors to each of the wires. Here is a picture of the wires – ignore the relay for a moment.

http://forums.pelicanparts.com/uploa...1526268748.jpg

33. Take the two wires of the same colour from b) above and twist them together. Crimp another female blade connector onto these two wires. NOTE that the three pins on the motor are very close to each other, you may want to use ‘bare’ crimped connectors with shrink wrap

34. Crimp female blades to the two remaining wires from b) above. Here is the finished product – again, ignore the connections to the motor for the moment; however do take note of how close the pins are.

http://forums.pelicanparts.com/uploa...1526268802.jpg

http://forums.pelicanparts.com/uploa...1526268802.jpg

35. To make things tidy, use zip ties and cable wrap if you have it available to bundle the wires together neatly.

36. Connect the wires to the relay and motor according to the below diagram. The relay should have a wiring diagram printed on the outside of it to help.

http://forums.pelicanparts.com/uploa...1526268855.png

- The top four pins are the ‘inputs’ – two for the solenoid (the topmost pins), and two for the motor.
- The bottom four pins are the ‘outputs’. The two wires that have a shared connection to the centre pin of the motor, are diagonally across from each other.
- Once you have everything wired together, you can test and ensure it all works correctly. Some troubleshooting hints are below.

37. The final result should look something like this. I haven’t quite terminated all of the wires to the car yet in this picture. Note the length of the wires – you don’t want too much wiring to have to fit behind the rubber housing!

http://forums.pelicanparts.com/uploa...1526268902.jpg

38. Put the small cover back on the motor to cover the three pins. Attach the backplate/motor assembly to the tin plate/rubber housing (you’ll need to temporarily disconnect the mirror connections to slip it through the tabbed opening.

http://forums.pelicanparts.com/uploa...1526269018.jpg

39. I took the rubber protective covering that was around the original motor assembly (pictured in Step 15 above), cut it, and wrapped it around the relay with a zip tie to provide some basic waterproofing. It’s visible in the picture below.

40. Take the mirror assembly back to the car and plug in the connections. Turn on the ignition and test.

http://forums.pelicanparts.com/uploa...1526269066.jpg

41. IMPORTANT NOTE: Due to the three-pin design of the motor, it is an ‘expected’ limitation that Up/Down is reversed when Left/Right is working correctly. I.e., when you press Down, the mirror will move Up and vice versa. Rectifying this would require breaking the shared connection on the middle pin of the motor, and soldering on separate connections for each motor. I was not willing to do this, as I want to be able to easily ‘plug and play’ replace the motor in the future if it dies; I also very quickly adapted to the new configuration and don’t even notice it anymore.

42. Troubleshooting:
a. If Left or Right moves when Up or Down is selected, reverse the two outer connections on the motor.
b. If Left moves when Right is selected, reverse the motor wires on the relay (Blue + Black and Black/Green)

43. Some measurements of the relay, in case you can’t get the same one as I did. It needs to be fairly small (a ‘micro-relay’) to fit behind the rubber housing.

http://forums.pelicanparts.com/uploa...1526269129.jpg
http://forums.pelicanparts.com/uploa...1526269129.jpg

44. The finished product!

http://forums.pelicanparts.com/uploa...1526269129.jpg

NOTE ON 3D PRINTED BACKING PLATE:

After completing this work, I noticed that my mirrors vibrated much more than they used to. I determined it was because the backing plate that I fabricated from a cookie tin was too thin (quel surprise). So, I used these plates as templates and created 3D printed plastic backing plates instead. They look really sharp (not that anyone will ever see them) and have eliminated the vibration. You can download them here and here. If you don’t have a 3D printer, there are many places online where you can send the STL file and they will print them for you very economically.
Here are the tinkercad links:

https://www.tinkercad.com/things/cWfzYQQeyQl
https://www.tinkercad.com/things/2z399w4zmiu

If you do go this route, there are two small modifications to the above instructions:

1. Replace the 6x M3x35mm bolts used to mount the motor to the plate with M3x40mm bolts.
2. The design includes 3x 4mm washers which should go between the backing plate and the motor, in order to provide clearance for the motor to move.

http://forums.pelicanparts.com/uploa...1526269266.jpg

Wow. Very impressive and informative. Thank you for the information and sourcing.

Very good job :)


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My mirrors have a short. I suspect the painters may have pinched a wire.
While searching, I stumbled across this. Very impressive!!!

As I was searching Pelican for mirror wiring info on my 83, I came across this post. In checking every component of my mirrors, I found the pivot point in the plastic housing where the spring and string mech is attached had a broken ear. This explained why the mirror would move and then jerk in certain directions. Since the cost of a new or used flag motor assembly would easily exceed the cost of the jetta motors used by the original poster, I figured Id give this conversion a try. All I have to say is its spectacular and hats off to the OP for figuring it out. I was able to source the Jetta motors for $45 a pair with wiring and a switch. There was no way to make the switch work in the car so I went with the relays as done above. I made a couple small changes. I found a very small 10a PCB mounted relay and chose to solder the wires direct as I didnt like all the crimp connections. It is mounted to the backing plate to reduce vibration on the leads. I also moved the connection outside of the mirror so you dont have to pop the pins to remove the mirror. Instead of drilling the mirror plate on weird angles, I made a plate from some scrap aluminum. Heres some pics of my mod. The relays have been coated in liquid electrical tape since these were taken.http://forums.pelicanparts.com/uploa...1636253648.jpg
http://forums.pelicanparts.com/uploa...1636253648.jpg
http://forums.pelicanparts.com/uploa...1636253648.jpg

Great job :)


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