ROG100

John,
My educated guess would be that the "Twin Dizzy" 16v cars use the later 85 to 88 foil.
Roger

pjg

84 euro vin lists 84 part # 928 641 973 01

Opelotus

UPDATE: picked up some more wire at Radioshack, the 18 gauge I bought last time was too large for the d-sub connectors and a bit overkill for the wiring of the cluster, so I got some 22 gauge red, black and green. To minimize cost, I will probably just use red for power, black for ground, and green for signal. Yes it's not ideal, but I want to get this conversion done by Monday so I can test it out. I also swapped the 15 pin d-sub connectors for some 25 pin units because the pins larger and are positioned in two rows rather than three, so they will be easier to solder.

Until I get some red LEDs I decided to keep the incandescent bulbs. I have white LEDs but they make the warning lights look washed out.

I was about to start wiring power to all the necessary components, using the old circuit film to determine the polarity of the components, when I came across something odd. The actual power distribution on the cluster differs from what is depicted in the wiring diagram. What gives? Does it really make a difference where power is taken from? I drew up two quick diagrams for comparison.

Opelotus

Since all the power feed wires for the cluster lead to the same fuse which is provided power when the key is on, I rewired the cluster in a way that makes more sense. Rather than have a bunch of devices powered by one pin on a connector and another pin powering only one device, I split it up differently.

Here's a photo of what it looks like so far, the volt/oil gauges and all the lights on the right side of the cluster are ready to go, still need to finish the temp/fuel side and the tach/speedo. Right now it looks pretty messy, and it is, I already have some ideas for improving it. We'll see how it looks once I add some zip ties to tidy it up a bit. Then I will solder on the mating connectors to the car's wiring harness and test it out!

cpayne

I say we go for an update. Hans could probably pull this off

http://www.youtube.com/watch?v=51U1KiNUlTo

jleidel

Looks great so far. A few questions/comments...
- what type of solder are you using?
- Looks like a 25-pin LPT standard connector. If your harness connectors are still in good shape, you can probably make an LPT-to-928 adapter by hacking an old printer cable. [see the IEEE-1284 standard pinout here: http://www.interfacebus.com/Design_Connector_1284.html].
- This looks really close to a "kit" in the makings... Roger, wink wink, nod nod!

Opelotus

Used .022" dia. 62% tin 36% lead 2% silver rosin core solder from Radioshack. Don't know much about the various types of solder so let me know what you think.

Yes, it is a 25 pin connector, much easier to work with then the HD 15 pin I purchased before since pins 1-13 are in one row, with pin 14 in the next row.

How do you propose I make said adapter? I was planning on cutting off the old 928 connectors and soldering on mating LPT connectors in their place. Then I was thinking it would be cool if I could find some computer extension cables with LPT male on one end and LPT female on the other (no crossover between pins, don't know if this even exists, could always make one) to plug in between cluster and car wiring harness so that the cluster can be easily accessible for adjustments/calibration outside the pod. Not sure if it is even necessary but it would be cool.

jleidel

Your solder looks fine for the project. Some solder variants are tougher to flow on small components...

I agree, this method would be really cool. You could easily use a 1ft cable as the basis for the permanent wiring and a 6ft cable for testing purposes. I also agree that disposing of the original proprietary connectors is probably a good thing. These things are a PITA.

DB25 M-F connector: http://www.cablestogo.com/product.as...=935&sku=03029

Opelotus

Cool, thanks for the input. If I'm lucky my dad will have at least one of those cables in the basement somewhere. I finished 2 out of 3 connectors on the cluster, still have to wire up the tach and speedo, then move onto the wiring harness.

bronto

Once this is "wired" someone should make a harness that can just be plugged in.

Opelotus

Do you mean a harness that plugs directly onto the back of the cluster and into the factory wiring harness plugs?

I just finished replacing the factory connectors in the car. Not the most fun job as the left hand harness doesn't have much slack so you need to work in a tight spot.

Plugged everything in and tested it out: all warning lights work, gauges work correctly, fuel and temp gauges no longer fluctuate when the parking lights are on or off. Only time will tell if accuracy has improved. Speedo works, but it dropped out for about 2 seconds at one point. I didn't give the connections to the gauges a thorough cleaning yet so I suspect this is the issue. Also the CASIS does not work STILL, I will recheck the wiring/continuity to the tach, hopefully that will fix it.

Finally there are a few adjustments to be made to the connectors. Right now they are too low and the steering wheel cannot be lowered without putting strain on the wires. I will also be installing plastic plugs with strain relief on the car's harness to protect the connections. Color coding will be added too.

I'll try to take some pics in the morning.

txhokie4life

There's a discussion on Pelican that hilighted the operation of the battery supply/ alternator
excitation circuit.

http://forums.pelicanparts.com/porsc...ml#post5779341

It basically puts the battery voltage on one node of the lamp and alternator on the other node.

If you replace this with a diode -- you won't get the same functionality.

If the alternator is too high -- you will not detect it as the diode works
only one way -- which would normally be alternator lower than battery voltage.

just something to iron out.

mike

Opelotus

Thanks for catching that! Luckily I left all the incandescent bulbs in until I figure out what I want to do with LEDs. Also my alt doesn't like to charge at idle with the lights and blower on, I wonder if there is an issue with the resistor/bulb/connections or if the engine ground just needs cleaning. Either way it's nice to know how the darn thing finally works/why unplugging the cluster disables the alternator.

txhokie4life

Somewhere I read you need -48 ohms across the lamp in parallel

A diode typically need -0.7v to pass current, Im not up on my LEDs

Which also means you'll get a 0.7v drop across a diode
So 12v in, 11.3 out

You might have to experiment to see if you can get it to work.

Not sure if you can wire two LEDs one backwards to catch the reverse polarity situation
But you would only catch a over voltage greater than the turn on voltage of tbd LEDs

Mike

Opelotus

yes there is a 68 ohm resistor in parallel on my cluster. I also considered using two LEDs as you mentioned. I guess it would be good to do some calculations using the formulas in the link you posted.