I don't think these early 78-81 clusters have gear position lights or indicators in automatic or manual.

tacho: pin 3M, green

dash illum: pin 12R, black/blue

did you confirm the ground, which is common for most of the lights, is clean at the body?

What diagrams are you looking at?

What is the condition of the signal processing box mounted underneath the dead pedal?

Hi Landseer
Thanks for responding

I am using the 80 Cannell.co.uk guide because I do not have an 80 Euro S flow diagram. I will try to contact porsche and see if they have something. Then cross referencing with 79 and 81 for comparisons and likenesses.

Tacho is 3m Green. So position 3 middle connector? The printed circuit label says the word "tacho" on L1, but the wire going there is not green so I will check 3 middle.

I went looking for the passenger side ground, in the wheel well, but fell short after removing the flap there, did not see it. I found the 14 pin up front and cleaned that. Cleaned the negative battery ground strap and all battery connectors. And cleaned the ground under the steering collumn. There were at least 8 brown wires going there. I will hunt down the other ground locations.

I do not know of the dead pedal or where it is yet.

Well, trace from pin 11R fried in the exact same spot again as in the picture.


The tacho has a green wire on 3M
The lights have indeed a blue/black on 12R
- I am getting continuity from this pin to the ground in the steering column with power off or on.

-Odo reset works and all lights work on exterior.

I dont think that is correct, so I must have a hot wire on the ground circuit right?

I do think the dash lights are wired correctly except there is a hot signal burning the lead off 11R an inch past the first bulb. So I still get that one rightmost 3w bulb only illuminated.

I now know the other ground location is behind rear right wheel, i was looking at passenger front wheel panel first.

If you are burning the trace off you have a short circuit someplace "downstream" of the failed area of the circuit. If I understand you issue you also have 2 of the 3 bulbs not lighting up in the instrument illumination? I would pull each of the bulbs and verify they are good by hooking them to a 12 v battery....a small alarm battery from say Radio Shack is a reasonable choice.....but don't stick it across the + and - terminals on the circuit board untill you have found your short. A bulb can fail "shorted" by the way, not often but they can.

Another suggestion I have is get the subject WSM wiring pages enlarged. I had mine printed out at Office Max in 18"x24" format, I think I will have them printed 24x36 next time. Makes troubleshooting a bit easier. I had about 11 pages blown up to the 18x24. Cost me a $1.60 per page...I am guessing that the UK has similar office print shops...

As others have pointed out there are other bulbs in the circuit that are controlled by the dimmer, like the clock light, the gear selsctor indicators on an auto transmission car, the radio backlight, and the ash tray light...

The net of it the 7 conventional "ground points" are not your problem but rather there is a point in the circut that is grounded that should not be.....and that is causing the foil to burn off your circuit board......

A lot of the dash lights trigger when powered by the Central Warning system.

Isn't there a fake pedal on the floor by driver's feet? Foot rest? Take it apart, the central warning box should be hidden inside. Its part of your circuitry.

I'm looking at USA wiring diagrams because Euro and USA shared most of the wiring and the CE panel.


Dash lights also are on the same circuits as the lights in the console I think. Lots of times mice or bad stereo installers mess-up the purple/black or blue/black wires in the console and cause the problems for the dash lights, but usually the fuse blows. Do you have the right fuses in the right slots. Never use an overrated one.

Looking at the '80 USA wiring diagram the 3 lights in question are pretty much directly in and directly out of the panel itself, with the positive connection being 12R and the ground being terminals 7R and 11R with 7 and 11 being connected together with an external jumper between them. I suffered a burnt trace of these lamps in my '84 also, but it was a result of me accidently shorting across the + and - conductors on the board. A lot of the rest of the instruments use the same grounds, since they are working correctly it would seem the cause of the burning conductor would need be on the other side of the bulbs but still on the board itself? Any possibility some one has put in the wrong bulbs for the 3 instrument illumination bulbs? Like maybe 1.5 or 4.5 vdc bulbs? Something is drawing excessive current and it would seem to be in the bulbs or the sockets themselves....

Thanks Tmpus and Landseer. I was in there a few hours today. I rebuilt both the german cluster and the english euro cluster. I repaired the burned trace from R11 just past the 1st immuminaton bulb.

If I put a continuity checker on R12 and R11 / R7 ( the two grounds) it lights up green meaning continuity. I do not know which ABC terninus on the CE the blue / black on R12 goes to. I tried a tone signal from my tester, but it goes everywhere since there is ground short.

I am fairly certain that the issue is with the blue black on R12.

I replaced all 3 illumination bulbs with 3W bulbs. I tested for illumination with a 9V battery each bulb before putting in. They do light up.

After repairing the burned trace, I used the tester on the middle speedo ring and the R12 pin. I have continuity across the cluster. I used a circuit pen, wasn't easy, I put tape behind the burn, then drew a new trace, then covered with tape on the front.

Do you guys know where the R12 blue / black cluster illumination lead terminates in the CE panel. If I can find, I can run a new one that I know is direct with no ground detours.

I still haven't found passenger side ground. There is one in the rear right hatch. One under steering column. Is it by the 14 pin under the hood?

Side note... Found the leveler switch
I had an 89 S4 which had hatch release left of the drivers seat. This 80 euro model has a dimmer switch that rotates right and left rather than lifting like the hatch release.

OK.

Ground bolt location isn't necessarily corresponding to the item grounded.

You should remove the wooden covers and passenger side tray above fuse box.

The grounds are on the firewall above the fuse box. Umm, same for S4. I can see the brown ground wires in the picture of your panel, above it.

Its more efficient in hunting down any electrical problem on a 928 if you have first done 4 things.
1. Remove, polish, inspect and re-fuse the CE panel. Confirm right relays in right slots and change the critical relays with new. (and seal the fan while in there)
2. Clean all grounds.
3. Remove the console side panels and look for rodent damage or melts.
4. Remove all aftermarket wiring

You did some good work with the terminal cleaning and refusing. Did you remove the panel to do it? It needs to come out now. Use of high amp fuses and melts means you could have melt cross circuits on the back of the panel, rendering any further work useless. If you had removed the panel (which really isn't as bad as it seems) you would have discovered the passenger grounds in the proceess. It will force you to look closely at each of the wires in each of the colored distribution plugs at the base of the panel. Great evidence there if you see insulation decay or melt.

On your panel picture, you still have one scabbed vampire wire connection on plug to the left, A or B?. Rid your car of that crap.


Read my 16V ground thread for more (at least skim the pictures, they will help some).

The wiring diagrams do a pretty good job of mapping the circuits. They define the grounds for each circuit, too. You just have to spend some time looking closely at them, all of them. It will save time in the long run.

I'll take a look and see what I can find regarding the instrumentation wire path to get you started. I think clock light and cigar lighter illumination also run on that circuit. That's where I've found problems on 4 different cars.

On 4 cars I've found badly melted wires. 2 have had wire melts behind the panel causing intermittent short circuits. All 7 have had corrosion on grounds. Very common occurences on cars that have lived lives where it rains.

So, interesting circuit.

I took a cursory look. Confirm what I say with diagrams.


Fuse 11 is 8 amp.


(Black / Blue wire color is used for illumination and other things. It is not exclusive to a particular fuse or use )

Here are items on fuse 11, which is 8 amp:

Fuse 11 outputs to Two black wires that leave the fusebox at B8.

One of those black wires from B8 feeds full power to the illumination of the headlight switch.

The other black wire from B8 goes to the potentiometer --- and part splits-off before passing through the potentiometer as a black wire with full power to drive the lights in the heater control and the A/C switch.

The part of the voltage that enters the Potentiometer --- black in, black/blue out.... leaves as a controllable voltage to 3 instrument illumination lights (via trace R12)
and also branches off as a black / blue wire for use by the clock illumination light in the center console



Now, grounds are local to the subcircuit being fed.

So fuse 11 sends power to various places as noted, and these accessories ground locally.

So the clock grounds on one of the two ground studs on the firewall above the fuse panel noted as ground point "6" on the diagrams.

The headlight switch illumination grounds at the steering column (ground point "3")

So do the three bulbs illuminating the instrument panel.

Headlight illumination and heater control / A/C button lighting does not vary with potentiometer. I don't see right-off where the ground is connected, but am pretty certain its also one of the grounds on the firewall above the CE panel.

Instrument illumination and clock illumination do vary with potentiometer.



It gets real interesting on cars where the fuses have been jacked-up like yours.

The melting generally occurs with in the harnesses, too, not just on the circuit board.

I've had to remove the insulation from harnesses to separate melted wires out and to patch the collatoral damage --- sometimes intermittent short circuits, sometimes permanent ones.

Can happen behind the panel, tool. Several times I've found the defroster wires melted into other wires of all types on the back of the panel.


The film on the pod is usually damaged from solder breaks or tears due to mishandling. If there is a burn, I think it comes from other root causes.


Pay special attention to the plugs on the CE panel. Any damaged wires or any scorch marks on the plugs (or adjacent to fuses) is very important evidence.



Pay attention to J5 on the CE panel, too. It feeds illumination to the other dash switches, feeds the mileage reset unit, and the lights associated with front and Rear cigarette lighters. The reason I mention it is its use. The cigarette lighters get hot and get a lot of manipulation, plus they have some heavy power coming from a separate circuit that drives their heating elements and its usually powered-up (IIRC) all the time --- and the little rubber wire caps get brittle ---- and the wires are all in close proximity ---- that crap is all ripe for shorting and cross feeding and even burning down the car. The front cigarette lighter in particular, with the tight fit of the removable ashtray, interference of the gear shift lever with removal of it, and the fact that Stereo installers have there "talented" hands in their looking for power to scab or just manipulating the area as they bungle with the stereo head..... all these factors point to needing to check it. The illumination of the gear selector area is another source of problems in the console on some cars, though I didn't see that light mentioned in the diagrams.

Thanks for the great info Landseer and the double post.

I did not remove the CE panel last time, just cleaned all contacts, like you say, there are signs of melting on red wires on the first few lettered connectors at bottom, will check out J5 as well.

There could easily be melting into the ground circuit. Even R12 illumination lead tests circuit complete when i touch the other lead to ground!

4 hours yesterday repairing both clusters, swapping known working tach into the german cluster. I even repainted the tach needle from the orange original tach to match the more fluorescent red of the german cluster. Getting very familiar with these clusters now. : )

Cluster warning lights seem to work since they must be on another circuit.

One thing is the clock does work and illuminates. This is one tough clock.

Pulled my instrument cluster from my '82 Euro.

several of my board connector traces are pealed back?
What is the general solution here?

Does anyone have a diagram of the instrument cluster connections?
I've got a 3 connector version -- not sure what year.

Not sure exact year
http://forums.pelicanparts.com/uploa...1297706367.jpg
http://forums.pelicanparts.com/uploa...1297706389.jpg
http://forums.pelicanparts.com/uploa...1297706427.jpg

thx,

Mike

It looks like yours is burned in exactly the same place as mine. Does your illumination work on the cluster? Yours should be 3 12 pin connectors I believe in teh 82 Euro. The labels on the circuit film have names for what they go to, usually in german, then match it up to your flow diagrams. PM me if you need, or google cannell.co.uk and porsche and you can download there. You may want to start your own thread / post so we can help you there and keep issues separate. We'll catch you on your thread.

started new thread....

I have the same issue after totally refurbing mine. No instrument illumination,no tach and no fuel or temp gauge. All the warning lights,clock and HVAC,dimming function work. I'll be watching for the outcome. Gunar

Here's what I did with mine. Scroll down the pics:

Porsche 928 Forums dot com - View topic - Pics of my First 928 and Current Project

Wow, GBGastowers, I would bet yours has same ground issue. Sounds like my nightmare all over again, lol.

MPDano, that is fantastic work, I will take a good look once home from work!

Why do you think its a ground problem?

My R7 and R11 short to R12. 7 and 11 are brown wires to looped grounds on the printed circuit, and
R12 illumination from pot. As you suggested, I also think wire melt somewhere is joining them. There is a stereo install as well. Splices abound. Many repairs in harness wires are hidden behind shrink tubing.