AJK

This is weird. What I'm about to describe applies only to the rear passenger side cluster, ie. tail light, brake light, turn signal , backup light.

All the bulbs are the proper wattage and filliment type. All connections have been cleaned. All bulbs function properly as individual bulbs, that is, when removed from the cluster and 12V applied.

Now here 's the weird part. Under various conditions, say, running lights on, activating the turn singal will cause BOTH the tail light and the turn signal to flash alternately. (both dimmer than normal) Also, ALL the lights show some current flow ie. very dim, when the turn signal is flashing. With all other lights out, the turn signal is dimmer on the passenger side than the driver's side. Somehow there is a connection between all of these lights but only under certain circumstances. I first noticed this problem because everytime I turned on the right turn signal AND stepped on the break, the central warning light came on.

Anyone had this problem? Anyone suggest solution?

Alan

Its a grounding problem - clean the ground points at the back ... if the ground isn't there the currrent flows back through the other bulbs connected to 'ground' .

Alan

AJK

Thanks Alan. I'll check that out.

AJK

Just to close out this thread I'd like to report the final work to resolve this problem.

Chasing all the grounds seemed like a good idea so I tore into all seven of them, including the one behind the right rear qtr window trim panel which requires removal of not only the trim panel but also the right rear seat and right seat trim. None of the ground points looked especially bad but I disassembled and cleaned anyway. All told took about 6 hrs. Result? Nothing! Same problem as before.

So I went back to the wiring diagram and saw that there was one point where all of the affected lights came together, besides the main ground. That point was at the bulb recepticle of the turn signal. So I futzed around with the socked and at one point noticed that I could turn on the right turn signal without also getting the other lights in the cluster to also blink dimly. Took the car on the road and for the first time since I've owned it I can use the right turn signal and the brake and not activate the central warning light.

Perhaps this is too much about nothing, sorry if I've gone on too long, but I feel like I have achieved a small victory. It feels good to finally fix something.

On to the next problem.....speed control, I think.

Randy V

A win is a win!

Pfunde

When you say speed control, do you mean cruise control ? My cruise control "died" when I took my 78 apart last year, and I'm thinking of getting into fixing that. I'm thinking of installing something new, but still use orig swicth. Has anyone done that ?

Alan

The later cars used a fully electric cruise control (no vacuum elements).

I think the later version works very well. Not sure how easy to retrofit, that way it would be all Porsche at a least. Many of the after-market systems (JC Whitney etc) are hideous ergonomically...

AJK - glad you fixed it... So it was where all the bulb grounds connect at one of the bulb sockets? how did you fix - solder/splice together?, add connectors?

Anyway... Randy's right - if it ends up working - You Win!

Alan

Pfunde

Alan, don't you think it's possible to install aftermarket or simular and still use the switch - I mean I have a guy that do all the electric maintenance of my recording studio, including my Harrison X console ( from 87 - and very analog ). I mean a switch is a switch right ?

AJK

Alan,

The problem (apparently) was with the socket for the turn signal bulb. The other three daisy chain to that one. I did not take the cluster apart since it looks like you have to remove the rear clip to get at it. I know, I know; this is a half-as fix but for now I'm just glad it works. If it acts up again at least I know where to look.

Pfunde,

Yes, I mean cruise control. There is a write up somewhere here. Most of the time the problem is in the "temostat" and is an electrical connection failure Hmmm! That's for the old cars.

Alan

It may be possible - but be careful of the switch configurations though - many of these have a switch plate or even a column stalk (arrgghh!) - so its not clear what actual switch configs they use.

I'm not sure how the early 928 systems worked - were the column stalks the same as later? On the GTS the CC stalk has just 3 SPST switches: Forward = "on/+ accellerate", Backward is basically "cancel" and up is "resume". Of course on a manual it also auto-resumes (very cool!).

Most US & Japanese systems have a seperate on/off switch for the whole system then column/wheel switches (for most of): set, accellerate/+increment, coast/-increment, cancel & resume all as seperate switches - mostly either 4 or 5 switches.

Assuming the early Porsche system is the same - you won't have enough switches on the stalk.

Besides the simple & intuitive controls of the Porsche system (at least the later one) seem better to me - the only thing I ever wished for was digitally adjusting speed (clik up/down in fixed increments) - but I got over it...

Alan

SharkSkin

There's really not much that can go wrong with it. The WSMs have an excellent set of troubleshooting steps that will help you isolate any bad components/wiring. If your stoplights work, the fuse to the cruise brain is good.

Many people, including myself, have resurrected dead cruise brains by simply resoldering the PCB.