springer3

My rear wing deployed and then refused to go back down. My wife's diagnosis was Viagra overdose!

The motor worked fine in both directions when hot wired. The mechanism was smooth, and the limit switches were fine. The wiring checked out. Porsche wants $250 for the control module, and even used ones were $150.

There was a $0.50 transistor in the controller that was blown, so the repair cost was 50 cents plus a couple days of my time. The schematics for the controllers are not published, so I had to trace the circuit and draw a schematic before I found the problem.

Two things:

1) The German transistor has a "333" marking, but looks identical to a 2N2222 general purpose switching transistor. WARNING: the collector and emitter are reversed in the 333, and if you substitute a 2N2222, it will smoke immediately. That is the reason for the two day troubleshooting exercise.

2) The controller is no big deal to fix. There is a quad op amp, and about seven transistors plus the two relays that drive the motor. Now that I have invested in this thing, I can troubleshoot and fix the things in minutes. Anyone have some bad spoiler controllers they want refurbished or are will to sell?

On US cars, the controller is located on the passenger compartment front bulkhead, under the passenger's foot well carpet. It is gray plastic, about 1" x 2" x 4", with a connector on the end. There is one Phillips screw holding it to the bracket.

TMH

Hey, thanks for the tip. No spoiler issues at the moment, but its always nice when someone who has taken the time to troubleshoot the system shares with the rest of the board.

... and now I know where to send mine if/when it ever goes out!

Tom

BGLeduc

FWIW, on my '90 USA spec C2, there are actually two boxes, IIRC.

One is the interface to the manual spoiler control on the console, the other that you described, is the main controller.

I recently had the same problem, but it was due to sloppy wiring on my part when I installed a subwoofer amp under the seat. The wiring was not secured, and the seat actually severed one wire, and chaffed another while moving back and forth.

But before I found that, I got to inspect ALL of the spoiler mechanism, the end switches, etc. I had posted previously about that.

There is also a TSB available on ALLDATA that discusses an update to the controller that changes the functionality slightly.

Nice work on your part to fix it! Perhaps you could do the same with the aircon controllers. Seems to be a lot of problems with those and there very expensive to replace.

BGL

springer3

I am interested in getting my hands on any available dead 964 control modules. In most cases, they are easy to repair on cars the vintage of the 964 and earlier. The newer cars are fill of computer data buses, and the electronics are surface mount, multi-layer boards, and so complicated that it is impossible to analyze or repair..

My experience with fixing controllers is actually because of the troublesome and expensive aircon controllers in the W123 and W124 Mercedes. Anyone have some dead 964 control boxes they are willing to give up? With the box and the car wiring schematic, there should be no problem reverse engineering the things, especially if they are similar to the Benz units. I am not an electronics professional, but it is a hobby and I can get professional results.

BTY, Mercedes uses cheap components in their control boxes, and if you upgrade the components, the repaired units will outlast a brand new one. Porsche uses much better components in the 964 than Mercedes does in the E-class. I guess it helps to be top of the line, instead of a middle line model.

Adrian

1989 and 1990 have two control units related to the rear spoiler. One opens the sopiler at 80 kph (50 mph) the other is an emergency standy control unit which opens the spoiler at 115 kph (72 mph) if the first one fails. This system was removed for model year 1991.
1989 and 1990 models the spoiler control units are under the right seat. 1991 and up models the control unit is under the dash where the central locking unit is located in a 1989 and 1990 model.
Ciao,
Adrian
911C4

colo964

springer3,
I have recently developed the morningwood syndrome. The motor works up and down with hot wire, the microswitches work, and speedo wire has continuity (cruise control works, so I'm thinking the sender if fine). I opened the controllers. Mine is a 90' and has 337 transistors (not 333's), but no obvious burning or broken connections. Any ideas?

springer3

I am not familiar with the 2-module '90 controller, only the single-module version. Always check the continuity of the wiring harness first (finding a loose wire after buying an expensive module teaches that). If your spoiler is going up when it should not, the "up" relay is getting energized for some reason.

Find the module that has the two heavy-duty relays. The likely suspect is the transister driving the "up" relay. Mine was blown, but it was not crispy and could not be identified as blown. Crispy came later when I put in the 2N 2222 in the same orientation as the German transister. I cooked three before discovering that the 2N 2222 has the emitter and collector reversed from the German version. Find the suspect transister by tracing the terminals for the relay coil. One side is connected to ground, and the other is connected to the emitter of the suspect transister. Good luck.

Lorenfb

"Find the suspect transister by tracing the terminals for the relay coil."

OR,

1. the bad I.C.s (timer, op amp)
2. shorted/open capacitors
3. open circuit track
4. intermittent solder connections
5. bad relay coil winding
6. etc.

springer3

1. the bad I.C.s (timer, op amp) possible, but these are robust components and not stressed in this application
2. shorted/open capacitors possible, they are electrolytic about the right age to start failing. They usually leak goo when going bad

3. open circuit track not likely, Germans build really good circuit boards.

4. intermittent solder connections very possible, Germans have no clue how to make reliable solder joints. Also not easy to see a bad solder joint.

5. bad relay coil winding would not cause the relay to latch in.

6. etc. The transister is heavily-stressed, and the symptom is consistent with a shorted switching transister.

Lorenfb

"The transister is heavily-stressed, and the symptom is consistent with a shorted switching transister."

Kinda like replacing the 964 alternator when the car won't START because they are
"heavy-stressed" and "do" fail. Using the "shotgun" approach to troubleshooting rarely
works and usually causes more problems.

Actually, the coil driver is a BC337 rated at 500ma & 50 volts. It only drives the
relay coil (resistance ~= 100 ohms) for about 100ma and is protected from
overvoltage by a zener diode, and thus not really "heavy-stressed".

springer3

The replacement transister costs less than $1. It takes less time to swap it than it takes to troubleshoot. It is easy. It fixes the problem most of the time if the symptom is a sticking relay. The transister fails because it is highly stressed. It gets hot, and gets a kick from the relay coil.

I agreed with most of your alternaitive suggestions. I tried to help someone. Why the problem?

Lorenfb

"The transister fails because it is highly stressed. It gets hot, and gets a kick from the relay coil."

1. Gets hot???? - It's satuarated: Power = Vce (.50) X 100ma = 50mw
2. Gets a kick???? - It's protected by a zener diode: Vzener = 22 volts, Vce = 50 volts

Bottomline: It's inappropriate to suggest electronic component replacement,
without as a minimum the testing of that component first, becauae of potential:

1. damage to the circuit board,
2. incorrect component replacement type, or
3. incorrect component installation.

Muf

Hi, I have bought my 964 a few days ago, with a non-working spoiler. It did come up some times when controlled manually but not always.
Anyway, I took the control unit out in case I could see something obvious. The housing was melted. I had trouble opening the unit and I thought it is broken anyway so let's see what is inside. I am afraid I screwed it up :-( As it was so bent I could not take the circuit out easily and I have broken the connector plate.
Am I done for? Do you still wish to lay your hands on it? I can send it to you. :-)
(I know, I should have sent it before I messed with it, but this is me) :-(

Muf

Well, we have replaced every electronic part in the controller. Now it works much better but still not prefectly. The manual control works fine. The automatic raises the spoiler when 90km/h are exceeded but this is accompanied by a ref warning sign on the dashboard for about three seconds. When the spoiler is up, the lights go off. The spoiler does not return when I stop the car.
Does this look like a (still) faulty control unit or maybe something with the switches in the wing?
Thanks

springer3

Pinout for controller, 1992 version:

1 No connect
2 No connect
3 Spoiler moter terminal 2
4 Spoiler moter terminal 1
5 Earth/Ground
6 +12 through 15 amp fuse, always on
7 +12 from J25, switched (7.5 amp fuse)
8 F57 on central informer
9 Terminal 3 "extend" on manual switch, "spoiler up" limit switch
10 Terminal 5 "retract" on manual switch, "spoiler down" limit switch
11 Common on manual switch
12 G56 - speed signal
13 No connect
14 No connect

To check the motor, wires, and limit switches from the controller plug:

Limit switches and wiring:
Spoiler down, 9 - 11 open, 10 - 11 closed
Spoiler up, 9 - 11 closed, 10 - 11 open
Spoiler mid position - 9 - 11 and 10 - 11 open

Motor and wiring:
CAUTION: you will damage the motor or the mechanism if you drive past "full up" or "full down"
Put +12 and neg on 3 - 4. Polarity determines motor direction.


To check controller operation on work bench:

Put fused 12 volt power on 6 and 7, neg/ground on pin 5
If either relay operates, replace the driver transistor

Jumper pin 3 to pin 11, the "extend" relay should operate. Jumper pin 9 to pin 11, and the relay should drop out.

Jumper pin 10 to pin 11, the "retract" relay should operate. Jumper pin 10 to pin 11, and the relay should drop out.

If you have a function generator, you can put a pulse signal on pin 12 and simulate the auto-extend and auto-retract.