jserio

I am going to try an attach 2 pics to this thread. If it does not work then look in the picture section as I will put it there. I am trying to identify a brown and blue wires. My headlight motor is not operating so this is all part of my never ending quest to find out why. These wires are not connected to anything but come from the harness that goes to the dimmer plug on the column switch. Can anyone help me out on this. There is another pic that shows the dash dimmer bypassed, a small group of wires that have a brown and a blue, the headlight dimmer plug and the 2 unconnected wires. Please have a look.

jserio

Only the one uploaded. You can see the blue and brown wires. Also, Does anyone know which of the wires on the fat plug has anything to do with the headlight motor?

Steve Cattaneo

Solid brown wires on a Porsche are grounds.


The motor wires color code are, white/ black stripe, green/ yellow stripe, brown/red stripe, red/white stripe. The instrument dimmer wires are black/blue stripe, fused # 44 black wire. Check fuse #39, 38, 31 and 32. Remove and reinstall relay # XXIV light combination switch to clean the terminals. Clean and check ground points MP1 and MPII head lights main ground wires one is by the motor and the other on the opposite side.

jserio

Brand new relay. New good motor.

So could you say that a white/black stripe wire on the motor be the same color thru the light system? And pretty much with any electrical wire of any system? Or do they change in some fashion. This is a big part of electrical that stumps the hell out of me.

Hey Steve, I pretty much have brown figured out . Any idea on the blue or is yours not connected either?

Dozman

I believe that blue and brown wire is used on Euro models rear fog light. Does this sound correct Steve?

jserio

That could make sense since my rear fog is not working currently. I will check when I get the car back.

SteveCo

Joe;
Just wondering if you have the wiring diagrams for your car. While a little overwhelming at first, these are essential to electrical troubleshooting. I tried getting by without them when I first got my car, but quickly realized I would be too old to drive the car if I continued troubleshooting without the workshop manuals and the wiring diagram.

If you have the wiring diagrams, I'd be happy to help you try to decipher them. I learned from others on the board and an happy to share the knowledge.

Regards,
SteveCo in St. John's

jserio

Thanks Steve. I have the manual on disk but it is hard to blow up the picture of the wires and follow them. It is overwhelming to say the least. When I get the car back I think I will take you up on the help.

SteveCo

Joe;
I hear you on the disk-based wire tracing. I find it helpful to print out the sheets on paper, stick them together to make a nice contiguous diagram and then use colored highlighters to trac down the wirings I am after. I can do a bit on the screen, but this is definitely a job for paper and pen.

Let me know if I can help in any way.

Regards,
SteveCo in St. John's

jserio

Thanks Steve, I will do that for sure. I have one question while the car is not here. From what I have gathered the Red/White stripe wire on the motor activates the actual cycling. My question which I have not been able to get an answer to is: How can I make the motor cycle the correct way from outside the headlight switch.? Now I can put positive power to the spade and make the headlights go up and down continuously. What can I put power to to make the headlight motor cycle to the up position to see if I still have a headlight low beam problem? This I would like to try.

SteveCo

Joe;
I'll have to take a look at the wiring diagrams to try and figure this one out. Couple of background and related questions first, however:

1. Can you fill me in on the problem you are trying to solve? Headlights would not pop up? Headlights pop up but would not work? Previous owner messing with the wiring? Somethings else?

2. Have you started with the basics like fuses (testing, cleaning replacing), relays (testing, cleaning, swapping, checking terminal connections on the back of the CEP) and verified that you have input power at the right places on the central electric panel (CEP)?

3. You mentioned that the light motor is new. Does this mean that the old one was definitely bad or just was not operating properly. In other words why was it replaced?

If the problem "just started" chances are that it may be related to one of the subsystems controlling the headlights (power, relay, headlight switch, etc.). One major rule of 928 electrically troubleshooting is to start with the basics and ensure all is good there before tearing into the down stream components.

One valuable piece of advice I was given early on was to spend some time verifying and cleaning all the fuses and relays in the panel. 9 times out of 10 you will find incorrect fuses and oxidized terminals that rectify many issues by doing this work. Check the archives and you will find lots of info there about how to tackle this job. If you have not done this, I strong recommend you do.

I'll take a look at the diagrams and see if I can help out with your direct question, but you could easily be chasing your tail if you have not verified the core components first.

Regards,
SteveCo in St. John's

SteveCo

OK, let's have a go at this. You're original ask was wrt to the headlight motor not operating, so I will start there.

Some basics first: the headlamp motor is powered thru fuse 27 (15 amp fuse)...the headlight bulbs are powered through fuses 31/32 and 38/39 (7.5amp fuses). Check all these first to make sure they are good and have clean contacts and are firmly inserted. Check to ensure you have a good ground at the headlight motor harness as well.

The headlamp motor is fed from CEP bus# 30 through fuse 27 to combi relay terminal 30a, through the relay to terminal 30M, out through terminal P13 on the CEP and one to the motor via the large red/black stripe wire on the motor wiring harness.

To troubleshoot this system I would suggest:
1. Check for power on either side of Fuse 27
2. Pull the combi light relay (a real pain - read the archives for info on how to pull this...a dedicated relay puller is a real asset) and check for 12v power on terminal 30a.
3. Check for continuity between rely terminal 30M and CEP terminal P13 (plugs at the bottom of the CEP addressed from A to W with no "I" from left to right...right hand side of the plug, 3rd terminal from the bottom). Also check for continuity from P13 to the headlight motor terminal 30.

You could try jumping terminals 30a and 30M (see the archives for how to build a jumper) at the relay socket. This should cause the headlight motor to cycle up and down continuously. If this works, the problem you have is with the light control circuits or the motor control mechanism (which is built into to motor...unlikely this is the problem if you have replaced the motor). Maybe you have done this already.

After that, I'd target the headlight switch and rule that out, since it starts the process of activating the headlight motor. Most likely the problem is with the combi relay, so if you can test or replace that, it would be the logical first step.

You asked about a red/white wire. I cannot find one connected to the headlight system...maybe I am missing somthing here.

Regards,
SteveCo in St. John's