Hawkeyes

Every once in a while my '89 S4 instrument panel goes fubar - pics 1 & 2 are representative. (Sorry for poor quality, took it with my cell)

When I shut off the car, wait for instrument panel lights to go off, then restart, everything comes back to normal.

Do I need a new panel? Something shorting out? Anyone else had this problem?

Thanks,
Hawk

928ntslow

Sorry to say, but you need a new circuit board. I can guess at what little bits on the board are bad, but that won't help you. I'm guessing the reason the issue clears when you restart the car is that the electron build up is released when the current flow is reduced. Not sure if this is fixable or even worth fixing.

Best of luck. I hope I am wrong in the long run for your sake.

Hilton

Given the display electronics are driven by circuit boards inside the instrument panel, the problem is inside the panel itself, rather than the contacts on the back where the plugs connect.

As its not a problem I've seen reported here before, I'd say its a pretty safe bet its not software related, so its likely to be either a failed component or a broken trace or solder joint.

Finding an '89 replacement panel might be tricky.. or expensive if you have to get it from Porsche (is it available?). Replacing the instruments also means (if you don't get a new one with <100 miles on it) that you'll be stuck with the wrong mileage displayed, as the chips that hold it are in the panel.

I'm not sure whether 90+ instruments will fit an '89 (they have extra lights for airbag, PSD etc.)? If 90-95 car panels can be used it'll make finding one from a dismantler easier.

The other option if you're competent at soldering is to open it up and examine it.. and re-flow any dodgy looking solder, but I'd wait until the problem is persistent rather than intermittent in case of damage.

Leon Speed

New 89 S4 circuit boards are available from Porsche. I replaced mine recently. Costs about $850. Maybe check with our 928 parts suppliers first?

The mileage will start from 0 on a new board..so I now have a ultra rare 4657 mile 89 S4

Hilton

Bit late for Aryan, but for the interest of any others who replace their digital dash's circuit board, its possible to set the mileage on new boards (under 256 kms or 256 miles) as a one-time operation.

Pages 90-59 to 90-61 of the WSM detail how to do it.

Note that once its been set to a value higher than 256 its locked and can't be changed again using the controls.

pmooradian

I've seen the problem about 4 - 5 times over the past several years. As you saw, it goes away after you shut the car off and the display resets. It hasn't seemed to be a problem that recurs very often, maybe once or twice a year. I won't worry about it too much unless it starts to rear its ugly head on a regular basis. The only concern would be at what point Porsche discontinues the '89 circuit boards, as its done with some of the older 928s. If you don't replace it, it becomes a problem in the future, and the circuit boards are NLA when you go looking for one, you're up a creek or you'll have to look for a used one and hope for the best.

Leon Speed

Crap. That's what you get when you let somebody else a.k.a. a "professional" do your job. Another shop off the service list. Even at Porsche they forgot to screw the flappy solenoid back on the TB cover when they did the TB. I think I'll do everything myself from now on. Seems like I'm the only one who really cares about if it's done right.

ColinB

Hawkeyes
If everything else is working normally then unfortunately you do most likely have a failing circuit board. But odd symptoms, especially intermittent ones can also be caused by dirty connections (clean the contact strips with a pencil eraser) and poor grounds. A weak battery might do it too but then you would have difficulty starting the engine.

Aryan
3 years ago Porsche had only 4 new boards left in stock in Germany and they were all late model (GTS type) P/N 928 641 991 30. At the time they were about $1300 so if you bought a new '89 one recently this must be new stock and I'd say you got something of a bargain. It's excellent news that this board is being stocked again because it was believed to be officially NLA. Since the correct '89 board for my car was already NLA at that time I hunted for a second hand replacement for over a year and finally found one with German warnings but otherwise perfect.

BTW, you couldn't have adjusted the elapsed Km on your odometer anyway. The facility to do that on the panel was only introduced in '91 but Erkka (Vilheur) says he knows of many backyard workshops in Germany that have equipment which can reset the odometer 'illegally'.

Colin. 89GT

Hawkeyes

Hi Keith,

Yeah, that was my worry - a bad board. Question is, what part is the "bad" part? In the exploded view below, it would appear to be 3, 4 or 7? Or 3 and 4 and 7?

#7 (Printed Circuit Board-92864197303) is available for around $110.
#4 (Module-92864199200) is $389.
#3 (Assembly:Electronics-928 641 991 1) is unavailable.

What should I be replacing?

Leon Speed

Hey Colin,

You're making me doubt..the service shop bought and installed it and put it on the bill for about $850 (current exchange rate). Took the instrument cluster out once to replace some bulbs and the print board looked very new. I can check with Porsche here if it's available if somebody wants to know.

Alan

Since its still displaying something and looks like its probably stable - I think it could very well be just a flaky connection - especially as its quite infrequent. A power drop out might quite likely cause some corruption - this could be an internal solder joint or just one of the power connections.

Initially I'd go for a round af connector cleaning and see where that puts you...

The fact that it doesn't happen much suggests the panel does not have a hard electrical fault... so connections are likely suspects.

Alan

928ntslow

#7 is likely not the issue as all that does is carry current to the respective lights and gauges. Your issue would seem to be in the #3 as that is where the hard circuit board is.

Shark Attack

thats not so bad...

ROG100

From my experiance with my GTS cluster its the Circuit Board.
The display is full bright so #4 is not the issue.
In my case it was a heat related problem with a dry soldered joint on the CB.
If I put the CB in the freezer for 30 mins the problem went away until the CB regained ambient temp - here in TX 90F.
Rich Antrade repaired my old CB, however I never tried it after buying the last CB from Porsche for $1000+.
After replacing the CB my problem was eradiacted. I reset my CB to the same milage as the original.
I have been colecting Digital clusters and have some options avaialble.
I also beleive the later units will work in the older - 89 - cars as it was a softwear upgrade only.
I also have a brand new CB - 928 641 991 33 in stock as well as used units.
Let me know if I can help?
Best,
Roger

Hilton

Colin,

After reading an excellent post of yours from a few years back (in this thread https://rennlist.com/forums/928-forum/206167-miles-to-kmh-can-it-be-converted-91s4.html#post2175222), I suspect you're probably the most knowledgeable person on dash software levels etc.

Are boards with newer software levels compatible with the older digital dashes? (i.e. are pin-outs, connectors etc. the same).

I'm asking as I'm wondering whether an instrument panel from a '90 or later car will work in an '89. That would give '89 owners like Hawkeyes and myself more options for replacing the instrument panels. If there's no clear answer, I'm happy to be a guinea pig - my car is an import to Australia and shows miles - I'd like to swap it for one thats only in km's.

Also, does anyone have a complete list of the different software levels that made it into production, and know whether US models have different software level numbers to RoW models? (the post linked above is the most complete list I've seen.. but still raises questions). If I can't use a 90+ panel, I can always attempt to upgrade my panel to a US software version so I can at least switch units and get speed/consumption figures in km.